I've seen them at least twice on /r/whatisthisthing, a good couple dozen times on the road, and these days, even in press photos: GMC trucks with custom square boxes on the back, painted dark blue, with US Government "E" plates. These courier escorts, "unmarked" but about as subtle as a Crown Vic with a bull bar, are perhaps the most conspicuous part of an obscure office of a secretive agency. One that seems chronically underfunded but carries out a remarkable task: shipping nuclear weapons. The first nuclear weapon ever constructed, the Trinity Device, was transported over the road from Los Alamos to the north end of the White Sands Missile Range, near San Antonio, New Mexico. It was shipped disassembled, with the non-nuclear components strapped down in a box truck and the nuclear pit nestled in the back seat of a sedan. Army soldiers, of the Manhattan Engineering District, accompanied it for security. This was a singular operation, and the logistics were necessarily improvised. The end of the Second World War brought a brief reprieve in the nuclear weapons program, but only a brief one. By the 1950s, an arms race was underway. The civilian components of the Manhattan Project, reorganized as the Atomic Energy Commission, put manufacturing of nuclear arms into full swing. Most nuclear weapons of the late '40s, gravity bombs built for the Strategic Air Command, were assembled at former Manhattan Project laboratories. They were then "put away" at one of the three original nuclear weapons stockpiles: Manzano Base, Albuquerque; Killeen Base, Fort Hood; and and Clarksville Base, Fort Campbell [1]. By the mid-1950s, the Pantex Plant near Amarillo had been activated as a full-scale nuclear weapons manufacturing center. Weapons were stockpiled not only at the AEC's tunnel sites but at the "Q Areas" of about 20 Strategic Air Command bases throughout the country and overseas. Shipping and handling nuclear weapons was no longer a one-off operation, it was a national enterprise. To understand the considerations around nuclear transportation, it's important to know who controls nuclear weapons. In the early days of the nuclear program, all weapons were exclusively under civilian control. Even when stored on military installations (as nearly all were), the keys and combinations to the vaults were held by employees of the AEC, not military personnel. Civilian control was a key component of the Atomic Energy Act, an artifact of a political climate that disfavored the idea of fully empowering the military with such destructive weapons. Over the decades since, larger and larger parts of the nuclear arsenal have been transferred into military control. The majority of "ready to use" nuclear weapons today are "allocated" to the military, and the military is responsible for storing and transporting them. Even today, though, civilian control is very much in force for weapons in any state other than ready for use. Newly manufactured weapons (in eras in which there were such a thing), weapons on their way to and from refurbishment or modification, and weapons removed from the military allocation for eventual disassembly are all under the control of the Department of Energy's National Nuclear Security Administration [2]. So too are components of weapons, test assemblies, and the full spectrum of Special Nuclear Material (a category defined by the Atomic Energy Act). Just as in the 1940s, civilian employees of the DoE are responsible for securing and transporting a large inventory of weapons and sensitive assets. As the Atomic Energy Commission matured, and nuclear weapons became less of an experiment and more of a product, transportation arrangements matured as well. It's hard to find much historical detail on AEC shipping the 1960s, but we can pick up a few details from modern DoE publications showing how the process has improved. Weapons were transported in box trucks as part of a small convoy, accompanied by "technical couriers, special agents, and armed military police." Technical courier was an AEC job title, one that persisted for decades to describe the AEC staff who kept custody of weapons under transport. Despite the use of military security (references can be found to both Army MPs and Marines accompanying shipments), technical couriers were also armed. A late 1950s photo published by DoE depicts a civilian courier on the side of a road wielding a long suit jacket and an M3 submachine gun. During that period, shipments to overseas test sites were often made by military aircraft and Navy vessels. AEC couriers still kept custody of the device, and much of the route (for example, from Los Alamos to the Navy supply center at Oakland) was by AEC highway convoy. There have always been two key considerations in nuclear transportation: first, that an enemy force (first the Communists and later the Terrorists) might attempt to interdict such a shipment, and second, that nuclear weapons and materials are hazardous and any accident could create a disaster. More "broken arrow" incidents involve air transportation than anything else, and it seems that despite the potentially greater vulnerability to ambush, the ground has always been preferred for safety. A 1981 manual for military escort operations, applicable not only to nuclear but also chemical weapons, lays out some of the complexity of the task. "Suits Uncomfortable," "Radiation Lasts and Lasts," quick notes in the margin advise. The manual describes the broad responsibilities of escort teams, ranging from compliance with DOT hazmat regulations to making emergency repairs to contain leakage. It warns of the complexity of such operations near civilians: there may be thousands of civilians nearby, and they might panic. Escort personnel must be trained to be prepared for problems with the public. If they are not, their problems may be multiplied---perhaps to a point where satisfactory solutions become almost impossible. During the 1960s, heightened Cold War tensions and increasing concern of terrorism (likely owing to the increasingly prominent anti-war and anti-nuclear movements, sometimes as good as terrorists in the eyes of the military they opposed) lead to a complete rethinking of nuclear shipping. Details are scant, but the AEC seems to have increased the number of armed civilian guards and fully ended the use of any non-government couriers for special nuclear material. I can't say for sure, but this seems to be when the use of military escorts was largely abandoned in favor of a larger, better prepared AEC force. Increasing protests against nuclear weapons, which sometimes blocked the route of AEC convoys, may have made posse comitatus and political optics a problem with the use of the military on US roads. In 1975, the Atomic Energy Commission gave way to the Energy Research and Development Administration, predecessor to the modern Department of Energy. The ERDA reorganized huge parts of the nuclear weapons complex to align with a more conventional executive branch agency, and in doing so created the Office of Transportation Safeguards (OTS). OTS had two principal operations: the nuclear train, and nuclear trucks. Trains have been used to transport military ordnance for about as long as they have existed, and in the mid-20th century most major military installations had direct railroad access to their ammunition bunkers. When manufacturing operations began at the Pantex Plant, a train known as the "White Train" for its original color became the primary method of delivery of new weapons. The train was made up of distinctive armored cars surrounded by empty buffer cars (for collision safety) and modified box cars housing the armed escorts. Although the "white train" was repainted to make it less obvious, railfans demonstrate that it is hard to keep an unusual train secret, and anti-nuclear activists were often aware of its movements. While the train was considered a very safe and secure option for nuclear transportation (considering the very heavy armored cars and relative safety of established rail routes), it had its downsides. In 1985, a group of demonstrators assembled at Bangor Submarine Base. Among their goals was to bring attention to the Trident II SLBM by blocking the arrival of warheads on the White Train. 19 demonstrators were arrested and charged with conspiracy for their interference with the shipment. The jury found all 19 not guilty. The DoE is a little cagey, in their own histories, about why they stopped using the train. We can't say for sure that this demonstration was the reason, but it must have been a factor. At Bangor, despite the easy rail access, all subsequent shipments were made by truck. Trucks were far more flexible and less obvious, able to operate on unpredictable schedules and vary their routes to evade protests. In the two following years, use of the White Train trailed off and then ended entirely. From 1987, all land transportation of nuclear weapons would be by semi-trailer. This incident seems to have been formative for the OTS, which in classic defense fashion would be renamed the Office of Secure Transportation, or OST. A briefing on the OST, likely made for military and law enforcement partners, describes their tactical doctrine: "Remain Unpredictable." Sub-bullets of this concept include "Chess Match" and "Ruthless Adherence to Deductive Thought Process," the meaning of which we could ponder for hours, but if not a military briefing this is at least a paramilitary powerpoint. Such curious phrases accompanied by baffling concept diagrams (as we find them here) are part of a fine American tradition. Beginning somewhere around 1985, the backbone of the OST's security program became obscurity. An early '00s document from an anti-nuclear weapons group notes that there were only two known photographs of OST vehicles. At varying times in their recent history, OST's policy seems to have been to either not notify notify law enforcement of their presence at all, or to advise state police only that there was a "special operation" that they were not to interfere with. Box trucks marked "Atomic Energy Commission," or trains bearing the reporting symbol "AEC," are long gone. OST convoys are now unmarked and, at least by intention, stealthy. It must be because of this history that the OST is so little-known today. It's not exactly a secret, and there have been occasional waves of newspaper coverage for its entire existence. While the OST remains low-profile relative to, say, the national laboratories, over the last decade the DoE has rather opened up. There are multiple photos, and even a short video, published by the DoE depicting OST vehicles and personnel. The OST has had a hard time attracting and retaining staff, which is perhaps the biggest motivator of this new publicity: almost all of the information the DoE puts out to the public about OST is for recruiting. It is, of course, a long-running comedy that the federal government's efforts at low-profile vehicles so universally amount to large domestic trucks in dark colors with push bumpers, spotlights, and GSA license plates. OST convoys are not hard to recognize, and are conspicuous enough that with some patience you can find numerous examples of people with no idea what they are finding them odd enough to take photos. The OST, even as an acknowledged office of the NNSA with open job listings, still feels a bit like a conspiracy. During the early 1970s, the AEC charged engineers at Sandia with the design of a new, specialized vehicle for highway transportation of nuclear weapons. The result, with a name only the government could love, was the Safe Secure Transporter (SST, which is also often expanded as Safe Secure Trailer). Assembly and maintenance of the SSTs was contracted to Allied Signal, now part of Honeywell. During the 1990s, the SST was replaced by the Safeguards Transporter (SGT), also designed by Sandia. By M&A, the Allied Signal contract had passed to Honeywell Federal Manufacturing & Technology (FM&T), also the operating contractor of the Kansas City Plant where many non-nuclear components of nuclear weapons are made. Honeywell FM&T continues to service the SGTs today, and is building their Sandia-designed third-generation replacement, the Mobile Guardian [3]. Although DoE is no longer stingy about photographs of the SGT, details of its design remain closely held. The SGT consists of a silver semi-trailer, which looks mostly similar to any other van trailer but is a bit shorter than the typical 53' (probably because of its weight). Perhaps the most distinctive feature of the trailers is an underslung equipment enclosure which appears to contain an air conditioner; an unusual way to mount the equipment that I have never seen on another semi-trailer. Various DoE-released documents have given some interior details, although they're a bit confusing on close reading, probably because the trailers have been replaced and refurbished multiple times and things have changed. They are heavily armored, the doors apparently 12" thick. They are equipped with a surprising number of spray nozzles, providing fire suppression, some sort of active denial system (perhaps tear gas), and an expanding foam that can be released to secure the contents in an accident. There is some sort of advanced lock system that prevents the trailer being opened except at the destination, perhaps using age-old bank vault techniques like time delay or maybe drawing from Sandia's work on permissive action links and cryptographic authentication. The trailers are pulled by a Peterbilt tractor that looks normal until you pay attention. They are painted various colors, perhaps a lesson learned from the conspicuity of the White Train. They're visibly up-armored, with the windshield replaced by two flat ballistic glass panels, much like you'd see on a cash transport. The sleeper has been modified to fit additional equipment and expand seating capacity to four crew members. Maybe more obvious, they're probably the only semitrailers and tractors that you'll see with GSA "E" prefix license plates (for Department of Energy). SGTs are accompanied on the road by a number of escort vehicles, although I couldn't say exactly how many. From published photographs, we can see that these fall into two types: the dark blue, almost black GMC box trucks with not-so-subtle emergency lights and vans with fiberglass bodies that you might mistake for a Winnebago were they not conspicuously undecorated. I've also seen at least one photo of a larger Topkick box truck associated with the OST, as well as dark-painted conventional cargo vans with rooftop AC. If you will forgive the shilling for my Online Brand, I posted a collection of photos on Mastodon. These were all released by NNSA and were presumably taken by OST or Honeywell staff, you can see that many of them are probably from the same photoshoot. Depending on what part of the country you are in, you may very well be able to pick these vehicles out on the freeway. Hint: they don't go faster than 60, and only operate during the day in good weather. These escort vehicles probably mostly carry additional guards, but one can assume that they also have communications equipment and emergency supplies. Besides security, one of the roles of the OST personnel is prompt emergency response, taking the first steps to contain any kind of radiological release before larger response forces can arrive. Documents indicate that OST has partnerships with both DoE facilities (such as national labs) and the Air Force to provide a rapid response capability and offer secure stopping points for OST convoys. There is, perhaps, a reason for the OST's low profile besides security and anti-nuclear controversy: classic government controversy. The OST is sort of infamously not in great shape. Some of the vehicles were originally fabricated in Albuquerque in a motley assortment of leased buildings put together temporarily for the task, others were fabricated at the Kansas City Plant. It's hard to tell which is which, but when refurbishment of the trailers was initiated in the 2000s, it was decided to centralize all vehicle work near the OST's headquarters (also a leased office building) in Albuquerque. At the time, the OST's warehouses and workshops were in poor and declining condition, and deemed too small for the task. OST's communications center (discussed in more detail later) was in former WWII Sandia Base barracks along with NNSA's other Albuquerque offices, and they were in markedly bad shape. To ready Honeywell FM&T for a large refurbishment project and equip OST with more reliable, futureproof facilities, it was proposed to build the Albuquerque Transportation Technology Center (ATTC) near the Sunport. In 2009, the ATTC was canceled. To this day, Honeywell FM&T works out of various industrial park suites it has leased, mostly the same ones as the 1980s. Facilities plans released by the DoE in response to a lawsuit by an activist organization end in FY2014 but tell a sad story of escalating deferred maintenance, buildings in unknown condition because of the lack of resources to inspect them, and an aging vehicle fleet that was becoming less reliable and more expensive to maintain. The OST has 42 trucks and about 700 guards, now styled as Federal Agents. They are mostly recruited from military special forces, receive extensive training, and hold limited law enforcement powers and a statutory authorization to use deadly force in the defense of their convoys. Under a little-known and (fortunately) little-used provision of the Atomic Energy Act, they can declare National Security Areas, sort of a limited form of martial law. Despite these expansive powers, a 2015 audit report from the DoE found that OST federal agents were unsustainably overworked (with some averaging nearly 20 hours of overtime per week), were involved in an unacceptable number of drug and alcohol-related incidents for members of the Human Reliability Program, and that a series of oversights and poor management had lead to OST leadership taking five months to find out that an OST Federal Agent had threatened to kill two of his coworkers. Recruiting and retention of OST staff is poor, and this all comes in the context of an increasing number of nuclear shipments due to the ongoing weapons modernization program. The OST keeps a low profile perhaps, in part, because it is troubled. Few audit reports, GSA evaluations, or even planning documents have been released to the public since 2015. While this leaves the possibility that the situation has markedly improved, refusal to talk about it doesn't tend to indicate good news. OST is a large organization for its low profile. It operates out of three command centers: Western Command, at Kirtland AFB, Central Command, in Texas at Pantex, and Eastern Command, at Savannah River. The OST headquarters is leased space in an office building near the Sunport, and the communications and control center is in the new NNSA building on Eubank. Agent training takes place primarily on a tenant basis at a National Guard base in Arkansas. OST additionally operates four or five (it was five but I believe one has been decommissioned) communications facilities. I have not been successful in locating those exactly besides that they are in New Mexico, Idaho, Missouri, South Carolina, and Maryland. Descriptions of these facilities are consistent with HF radio sites. That brings us to the topic of communications, which you know I could go on about at length. I have been interested in OST for a long time, and a while back I wrote about the TacNet Tracker, an interesting experiment in early mobile computing and mesh networking that Sandia developed as a tactical communications system for OST. OST used to use a proprietary, Sandia-developed digital HF radio system for communications between convoys and the control center. That was replaced by ALE, for commonality with military systems, sometime in the 1990s. More recent documents show that OST continues to use HF radio via the five relay stations, but also uses satellite messaging (which is described as Qualcomm, suggesting the off-the-shelf commercial system that is broadly popular in the trucking industry). Things have no doubt continued to advance since that dated briefing, as more recent documents mention real-time video links and extensive digital communications. The OST has assets beyond trucks, although the trucks are the backbone of the system. Three 737s, registered in the NNSA name, make up their most important air assets. Released documents don't rule out the possibility of these aircraft being used to transport nuclear weapons, but suggest that they're primarily for logistical support and personnel transport. Other smaller aircraft are in the OST inventory as well, all operating from a hanger at the Albuquerque Sunport. They fly fairly often, perhaps providing air support to OST convoys, but the NNSA indicates that they also use the OST aircraft for other related NNSA functions like transportation of the Radiological Assistance Program teams. It should be said that despite the OST's long-running funding and administrative problems, it has maintained an excellent safety record. Many sources state that there was only been one road accident involving an OST convoy, in which the truck slid off the road during an ice storm in Nebraska. I have actually seen OST documents refer to another incident in Oregon in the early '80s, in which an escort vehicle was forced off the road by a drunk driver and went into the ditch. I think it goes mostly unmentioned since only an escort vehicle was involved and there was no press attention at the time. Otherwise, despite troubling indications of its future sustainability, OST seems to have kept an excellent track record. Finally, if you have fifteen minutes to kill, this video is probably the most extensive source of information on OST operations to have been made public. Even though I'm pretty sure a couple of the historical details it gives are wrong, but what's new. Special credit if you notice the lady that's still wearing her site-specific Q badge in the video. Badges off! Badges! Also, if you're former military and can hold down a Q, a CDL, EMT-B, and firearms qualifications, they're hiring. I hear the overtime is good. But maybe the threats of violence not so much. [1] The early Cold War was a very dynamic time in nuclear history, and plans changed quickly as the AEC and Armed Forces Special Weapons Project developed their first real nuclear strategy. Many of these historic details are thus complicated and I am somewhat simplifying. There were other stockpile sites planned that underwent some construction, and it is not totally clear if they were used before strategies changed once again. Similarly, manufacturing operations moved around quite a bit during this era and are hard to summarize. [2] The NNSA, not to be confused with the agency with only one N, is a semi-autonomous division of the Department of Energy with programmatic responsibility for nuclear weapons and nuclear security. Its Administrator, currently former Sandia director Jill Hruby, is an Under Secretary of Energy and answers to the Secretary of Energy (and then to the President). I am personally very fond of Jill Hruby because of memorable comments she made after Trump's first election. They were not exactly complimentary to the new administration and I have a hard time thinking her outspokenness was not a factor in her removal as director of the laboratory. I assume her tenure as NNSA Administrator is about to come to an end. [3] Here's a brief anecdote about how researching these topics can drive you a little mad. Unclassified documents about OST and their vehicles make frequent reference to the "Craddock buildings," where they are maintained and overhauled in Albuquerque. For years, this lead me to assume that Craddock was the name of a defense contractor that originally held the contract and Honeywell had acquired. There is, to boot, an office building near OST headquarters in Albuquerque that has a distinctive logo and the name "Craddock" in relief, although it's been painted over to match the rest of the building. Only yesterday did I look into this specifically and discover that Craddock is a Colorado-based commercial real estate firm that developed the industrial park near the airport, where MITS manufactured the Altair 8800 and Allied Signal manufactured the SSTs (if I am not mistaken Honeywell FM&T now uses the old MITS suite!). OST just calls them the Craddock buildings because Craddock is the landlord. Craddock went bankrupt in the '80s, sold off part of its Albuquerque holdings, and mostly withdrew to Colorado, probably why they're not a well-known name here today.

So we all know about twisted-pair ethernet, huh? I get a little frustrated with a lot of histories of the topic, like the recent neil breen^w^wserial port video, because they often fail to address some obvious questions about the origin of twisted-pair network cabling. Well, I will fail to answer these as well, because the reality is that these answers have proven very difficult to track down. For example, I have discussed before that TIA-568A and B are specified for compatibility with two different multipair wiring conventions, telephone and SYSTIMAX. And yet both standards actually originate within AT&T, so why did AT&T disagree internally on the correspondence of pair numbers to pair colors? Well, it's quite likely that some of these things just don't have satisfactory answers. Maybe the SYSTIMAX people just didn't realize there was an existing convention until they were committed. Maybe they had some specific reason to assign pairs 3 and 4 differently that didn't survive to the modern era. Who knows? At this point, the answer may be no one. There are other oddities to which I can provide a more satisfactory answer. For example, why is it so widely said that twisted-pair ethernet was selected for compatibility with existing telephone cabling, when its most common form (10/100) is in fact not compatible with existing telephone cabling? But before we get there, let's address one other question that the Serial Port video has left with a lot of people. Most office buildings, it is mentioned, had 25-pair wiring installed to each office. Wow, that's a lot of pairs! A telephone line, of course, uses a single pair. UTP ethernet would be designed to use two. Why 25? The answer lies in the key telephone system. The 1A2 key telephone system, and its predecessors and successors, was an extremely common telephone system in the offices of the 1980s. Much of the existing communications wiring of the era's commercial buildings had been installed specifically for a 1A2-like system. I have previously explained that key telephone systems, for simplicity of implementation, inverted the architecture we expect from the PBX by connecting many lines to each phone, instead of many phones to each line. This is the first reason: a typical six-button key telephone, with access to five lines plus hold, needed five pairs to deliver those five lines. An eighteen button call director would have, when fully equipped, 17 lines requiring 17 pairs. Already, you will see that we can get to some pretty substantial pair counts. On top of that, though, 1A2 telephones provided features like hold, busy line indication (a line key lighting up to indicate its status), and selective ringing. Later business telephone systems would use a digital connection to control these aspects of the phone, but the 1A2 is completely analog. It uses more pairs. There is an A-lead pair, which controls hold release. There is a lamp pair for each line button, to control the light. There is a pair to control the phone's ringer, and in some installations, another pair to control a buzzer (used to differentiate outside calls from calls on an intercom line). So, a fairly simple desk phone could require eight or more pairs. With the popularity of the 1A2 system, the industry converged on a standard for business telephone wiring: 25-pair cables terminated in Amphenol connectors. A call director could still require two cables, and two Amphenol connectors, and you can imagine how bulky this connection was. 25-pair cable was fairly expensive. These issues all motivated the development of digitally-controlled systems like the Merlin, but as businesses looked to install computer networks, 25-pair cabling was what most of them already had in place. But, there is a key difference between the unshielded twisted-pair cables used for telephones and the unshielded twisted-pair we think of today: the twist rate. We mostly interact with this property through the proxy of "cable categories," which seem to have originated with cable distributors (perhaps Anixter) but were later standardized by TIA-568. Category 1: up to 1MHz (not included in TIA-568) Category 2: up to 4MHz (not included in TIA-568) Category 3: up to 16MHz Category 4: up to 20MHz (not included in TIA-568) Category 5: up to 100MHz Category 6: up to 250MHz Category 7: up to 600MHz (not included in TIA-568) Category 8: up to 2GHz Some of these categories are not, in fact, unshielded twisted-pair (UTP), as shielding is required to achieve the specified bandwidth. The important thing about these cable categories is that they sort of abstract away the physical details of the cable's construction, by basing the definition around a maximum usable bandwidth. That bandwidth is, of course, defined in terms of attenuation and crosstalk parameters that differ between categories. Among the factors that determine the bandwidth capability of a cable is the twist rate, the frequency with which the two wires in a pair switch positions. The idea of twisted pair is very old, dating to the turn of the 20th century and open wire telephone leads that used "transposition brackets" to switch the order of the wires on the telephone pole. More frequent twisting provides protection against crosstalk at higher frequencies, due to the shorter spans of unbalanced wire. As carrier systems used higher frequencies on open wire telephone leads, transposition brackets became more frequent. Telephone cable is much the same, with the frequency of twists referred to as the pitch. The pitch is not actually specified by category standards; cables use whatever pitch is sufficient to meet the performance requirements. In practice, it's also typical to use slightly different pitches for different pairs in a cable, to avoid different pairs "interlocking" with each other and inviting other forms of EM coupling. Inside telephone wiring in residential buildings is often completely unrated and may be more or less equivalent to category 1, which is a somewhat informal standard sufficient only for analog voice applications. Of course, commercial buildings were also using their twisted-pair cabling only for analog voice, but the higher number of pairs in a cable and the nature of key systems made crosstalk a more noticeable problem. As a result, category 3 was the most common cable type in 1A2-type installations of the 1980s. This is why category 3 was the first to make it into the standard, and it's why category 3 was the standard physical medium for 10BASE-T. In common parlance, wiring originally installed for voice applications was referred to as "voice grade." This paralleled terminology used within AT&T for services like leased lines. In inside wiring applications, "voice grade" was mostly synonymous with category 3. Indeed, StarLAN, the main predecessor to 10BASE-T, required a bandwidth of 12MHz... beyond the reliable capabilities of category 1 and 2, but perfectly suited for category 3. This brings us to our second part of the twisted-pair story that is frequently elided in histories: the transition from category 3 cabling to category 5 cabling, as is required by the 100BASE-TX "10/100" ethernet. On the one hand, the explanation is simple. 100BASE-TX requires a 100MHz cable, which means it requires category 5. Case closed. On the other hand, remember the whole entire thing about twisted-pair being intended to reuse existing telephone cable? Yes, the move from 10BASE-T to 100BASE-TX, and from category 3 to category 5, was not an entirely straightforward one. The desire to reuse existing telephone cabling was still very much alive, and several divergent versions of twisted-pair ethernet were created for this purpose. Ethernet comes with these kind of odd old conventions for describing physical carriers. The first part is the speed, the second part is the bandwidth/position (mostly obsolete, with BASE for baseband being the only surviving example), and the next part, often after a hyphen, identifies the medium. This medium code was poorly standardized and can be a little confusing. Most probably know that 10BASE5 and 10BASE2 identify 10Mbps Ethernet over two different types of coaxial cable. Perhaps fewer know that StarLAN, over twisted pair, was initially described as 1BASE5 (it was, originally, 1Mbps). The reason for the initial "5" code for twisted pair seems to be lost to history; by the time Ethernet over twisted pair was accepted as part of the IEEE 802.3 standard, the medium designator had changed to "-T" for Twisted Pair: 10BASE-T. And yet, 100Mbps "Fast Ethernet," while often referred to as 100BASE-T, is more properly 100BASE-TX. Why? To differentiate it from the competing standard 100BASE-T4, which was 100Mbps Ethernet over Category 3 twisted pair cable. There were substantial efforts to deploy Fast Ethernet without requiring the installation of new cable in existing buildings, and 100BASE-TX competed directly with both 100BASE-T4 and the somewhat eccentrically designated 100BaseVG. In 1995, all three of these media were set up for a three-way faceoff [1]. For our first contender, let's consider 100BASE-T4, which I'll call "T4" for short. The T4 media designator means Twisted pair, 4 pairs. Recall that, for various reasons, 10BASET only used two pairs (one each direction). Doubling the number of required pairs might seem like a bit of a demand, but 10BASET was already routinely used with four-pair cable and 8P8C connectors, and years later Gigabit 1000BASE-T would do the same. Using these four pairs, T4 could operate over category 3 cable at up to 100 meters. T4 used the pairs in an unusual way, directly extending the 10BASET pattern while compromising to achieve the high data rate over lower bandwidth cable. T4 had one pair each direction, and two pairs that dynamically changed directions as required. Yes, this means that 100BASE-T4 was only half duplex, a limitation that was standard for coaxial Ethernet but not typical for twisted pair. T4 was mostly a Broadcom project, who offered chipsets for the standard and brought 3Com on board as the principal (but not only) vendor of network hubs. The other category 3 contender, actually a slightly older one, was Hewlett-Packard's 100BaseVG. The "VG" media designator stood for "voice grade," indicating suitability for category 3 cables. Like T4, VG required four pairs. VG also uses those pairs in an unusual way, but a more interesting one: VG switches between a full-duplex, symmetric "control mode" and a half-duplex "transmission mode" in which all four pairs are used in one direction. Coordinating these transitions required a more complex physical layer protocol, and besides, HP took the opportunity to take on the problem of collisions. In 10BASE-T networks, the use of hubs meant that multiple hosts were in a collision domain, much like with coaxial Ethernet. As network demands increased, collisions became more frequent and the need to retransmit after collisions could appreciably reduce the effective capacity of the network. VG solved both problems at once by introducing, to Ethernet, one of the other great ideas of the local area networking industry: token-passing. The 100BaseVG physical layer incorporated a token-passing scheme in which the hub assigned tokens to nodes, both setting the network operation mode and preventing collisions. The standard even included a simple quality of service scheme to the tokens, called demand priority, in which nodes could indicate a priority level when requesting to transmit. The token-passing system made the effective throughput of heavily loaded VG networks appreciably higher than other Fast Ethernet networks. Demand priority promised to make VG more suitable for real-time media applications in which Ethernet had traditionally struggled due to its nondeterministic capacity allocation. Given that you have probably never heard of either of these standards, you are probably suspecting that they did not achieve widespread success. Indeed, the era of competition was quite short, and very few products were ever offered in either T4 or VG. Considering the enormous advantage of using existing Category 3 cabling, that's kind of a surprise, and it undermines the whole story that twisted pair ethernet succeeded because it eliminated the need to install new cabling. Of course, it doesn't make it wrong, exactly. Things had changed: 10BASET was standardized in 1990, and the three 100Mbps media were adopted in 1994-1995. Years had passed, and the market had changed. Besides, despite their advantages, T4 and VG were not without downsides. To start, both were half-duplex. I don't think this was actually that big of a limitation at the time; half-duplex 100Mbps was still a huge improvement in real performance over full-duplex 10Mbps in all but the most pathological cases. A period document from a network equipment vendor notes this limitation of T4 but then describes full-duplex as "unneeded for workstations." That might seem like an odd claim today, but I think it was a pretty fair one in the mid-'90s. A bigger problem was that both T4 and VG were meaningfully more complicated than TX. T4 used a complex and expensive DSP chip to recover the complex symbols from the lower-grade cable. VG's token passing scheme required a more elaborate physical layer protocol implementation. Both standards were meaningfully more expensive, both for adapters and network appliances. The cost benefit of using existing cabling was thus a little fuzzier: buyers would have to trade off the cost of new cabling vs. the savings of using less complex, less expensive TX equipment. For similar reasons, TX is also often said to have been more reliable than T4 or VG, although it's hard to tell if that's a bona fide advantage of TX or just a result of TX's much more widespread adoption. TX transceivers benefited from generations of improvement that T4 and VG transceivers never would. Let's think a bit about that tradeoff between new cable and more expensive equipment. T4 and VG both operated on category 3, but they required four pairs. In buildings that had adopted 10BASE-T on existing telephone wiring, they would most likely have only punched down two pairs (out of a larger cable) to their network jacks and equipment. That meant that an upgrade from 10BASE-T to 100BASE-T4, for example, still involved considerable effort by a telecom or network technician. There would often be enough spare pairs to add two more to each network device, but not always. In practice, upgrading an office building would still require the occasional new cable pull. T4 and VGs poor reputation for reliability, or moreover poor reputation for tolerating less-than-perfect installations, meant that even existing connections might need time-consuming troubleshooting to bring them up to full category 3 spec (while TX, by spec, requires the full 100MHz of category 5, it is fairly tolerant of underperforming cabling). There's another consideration as well: the full-duplex nature of TX makes it a lot more appealing in the equipment room and data center requirement, and for trunk connections (between hubs or switches). These network connections see much higher utilization, and often more symmetric utilization as well, so a full-duplex option really looks 50% faster than a half-duplex one. Historically, plenty of network architectures have included the use of different media for "end-user" vs trunk connections. Virtually all consumer and SMB internet service providers do so today. It has never really caught on in the LAN environment, where a smaller staff of network technicians are expected to maintain both sides. Put yourself in the shoes of an IT manager at a midsized business. One option is T4 or VG, with more expensive equipment and some refitting of the cable plant, and probably with TX used in some cases anyway. Another option is TX, with less expensive equipment and more refitting of the cable plant. You can see that the decision is less than obvious, and you could easily be swayed in the all-TX direction, especially considering the benefit of more standardization and fewer architectural and software differences from 10BASE-T. That seems to be what happened. T4 and VG found little adoption, and as inertia built, the cost and vendor diversity advantage of TX only got bigger. Besides, a widespread industry shift from shared-media networks (with hubs) to switched networks (with, well, switches) followed pretty closely behind 100BASE-TX. A lot of users went straight from 10BASE-T to switched 100BASE-TX, which almost totally eliminated the benefits of VG's token-passing scheme and made the cost advantage of TX even bigger. And that's the story, right? No, hold on, we need to talk about one other effort to upon 10BASE-T. Not because it's important, or influential, or anything, but because it's very weird. We need to talk about IsoEtherent and IsoNetworks. As I noted, Ethernet is poorly suited to real-time media applications. That was true in 1990, and it's still true today, but network connections have gotten so fast that the level of performance overhead available mitigates the problem. Still, there's a fundamental limitation: real-time media, like video and audio, requires a consistent amount of delivered bandwidth for the duration of playback. The Ethernet/IP network stack, for a couple of different reasons, provides only opportunistic or nondeterministic bandwidth to any given application. As a result, achieving smooth playback requires some combination of overprovisioning of the network and buffering of the media. This buffering introduces latency, which is particularly intolerable in real-time applications. You might think this problem has gone away entirely with today's very fast networks, but you can still see Twitch streamers struggling with just how bad the internet is at real-time media. An alternative approach comes from the telephone industry, which has always had real-time media as its primary concern. The family of digital network technologies developed in the telephone industry, SONET, ISDN, what have you, provide provisioned bandwidth via virtual circuit switching. If you are going to make a telephone call at 64Kbps, the network assigns an end-to-end, deterministic 64Kbps connection. Because this bandwidth allocation is so consistent and reliable, very little or no buffering is required, allowing for much lower latency. There are ways to address this problem, but they're far from perfect. The IP-based voice networks used by modern cellular carriers make extensive use of quality of service protocols but still fail to deliver the latency of the traditional TDM telephone network. Even with QoS, VoIP struggles to reach the reliability of ISDN. For practical reasons, consumers are rarely able to take any advantage of QoS for ubiquitous over-the-top media applications like streaming video. What if things were different? What if, instead of networks, we had IsoNetworks? IsoEthernet proposed a new type of hybrid network that was capable of both nondeterministic packet switching and deterministic (or, in telephone industry parlance, isochronous) virtual circuit switching. They took 10BASE-T and ISDN and ziptied them together, and then they put Iso in front of the name of everything. Here's how it works: IsoEthernet takes two pairs of category 3 cabling and runs 16.144 Mbps TDM frames over them at full duplex. This modest 60% increase in overall speed allows for a 10Mbps channel (called a P-channel by IsoEthernet) to be used to carry Ethernet frames, and the remaining 6.144Mbps to be used for 96 64-Kbps B-channels according to the traditional ISDN T2 scheme. An IsoEthernet host (sadly not called an IsoHost, at least not in any documents I've seen) can use both channels simultaneously to communicate with an IsoHub. An IsoHub functions as a standard Ethernet hub for the P-channel, but directs the B-channels to a TDM switching system like a PABX. The mention of a PABX, of course, illustrates the most likely application: telephone calls over the computer. I know that doesn't side like that much of a sell: most people just had a computer on their desk, and a phone on their desk, and despite decades of effort by the Unified Communications industry, few have felt a particular need to marry the two devices. But the 1990s saw the birth of telepresence: video conferencing. We're doing Zoom, now! Videoconferencing over IP over 10Mbps Ethernet with multiple hosts in a collision domain was a very, very ugly thing. Media streaming very quickly caused almost worst-case collision behavior, dropping the real capacity of the medium well below 10Mbps and making even low resolution video infeasible. Telephone protocols were far more suited to videoconferencing, and so naturally, most early videoconferencing equipment operated over ISDN. I had a Tandberg videoconferencing system, for example, which dated to the mid '00s. It still provided four jacks on the back suitable for 4x T1 connections or 4 ISDN PRIs (basically just a software difference), providing a total of around 6Mbps of provisioned bandwidth for silky smooth real-time video. These were widely used in academia and large corporations. If you ever worked somewhere with a Tandberg or Cisco (Cisco bought Tandberg) curved-monitor-wall system, it was most likely running over ISDN using H.320 video and T.120 application sharing ("application sharing" referred to things like virtual whiteboards). Early computer-based videoconferencing systems like Microsoft NetMeeting were designed to use existing computer networks. They used the same protocols, but over IP, with a resulting loss in reliability and increase in latency [2]. With IsoEthernet, there was no need for this compromise. You could use IP for your non-realtime computer applications, but your softphone and videoconferencing client could use ISDN. What a beautiful vision! As you can imagine, it went nowhere. Despite IEEE acceptance as 802.9 and promotion efforts by developer National Semiconductor, IsoEthernet never got even as far as 100BASE-T4 or 100BaseVG. I can't tell you for sure that it ever had a single customer outside of evaluation environments. [1] A similar 100Mbps-over-category 3 standard, called 100BASE-T2, also belongs to this series. I am omitting it from this article because it was standardized in 1998 after industry consolidation on 100BASE-TX, so it wasn't really part of the original competition. [2] The more prominent WebEx has a stranger history which will probably fill a whole article here one day---but it did also use H.320.

Histories of radio broadcasting often make a particular focus on the most powerful stations. For historic reasons, WBCT of Grand Rapids, Michigan broadcasts FM at 320¸000 watts. Many AM stations are licensed to operate at 50,000 watts, but this modern license limit represented a downgrade for some. WLW, of Cincinnati, once made 500,000. Less is made of the fun you can have under 10 watts: what we now call the Traveler's Information Station (TIS). The TIS was not formally established as a radio service until 1977, but has much earlier precedents. The American Association of Information Radio Operators, an advocacy group for TIS, has collected some of the history of early experimental low-power radio stations. Superintendent James R. McConaghie of Vicksburg National Military Park must have been something of a tinkerer, as he built a low-power AM transmitter for his car in the mid-1950s and used it to lead auto tours. He suggested that a tape recorder might be added to provide a pre-recorded narration, and so anticipated not only the TIS but a common system of narration for group tours to this day. During the New York World's Fair in 1964, a "leaky cable" AM system was installed on the George Washington Bridge to provide driving directions to visitors. This is the first example I can find of a low-power AM station used for traffic guidance. I can't find much information about this system except that it was the work of William Halstead, a pioneering radio engineer. Halstead is best known for developing FM stereo, but as we will see, he was a major force in TIS as well. The National Park Service continued to innovate in radio. Low-power stations offered a promising solution to the challenge of interpreting a park to increasing numbers of visitors, especially in the era of the automobile, when rangers no longer lead tour groups from place to place. In 1968, Yellowstone acquired six custom-built low power AM transmitters that were installed at fixed locations around the park. Connected to an 8-track player with a continuous loop cartridge, they broadcast park announcements and interpretive information to visitors approaching popular attractions. As an experiment, Yellowstone installed a five-mile "auto nature trail," a road with regularly spaced AM transmitters built for the experiment by Montana State University. The notion of an "auto nature trail" confounds our modern sensibilities, but such were the 1960s, when experiencing the world from the interior of your car was an American pastime. In a 1972 article on the effort, park service employees once again pointed out applications beyond park interpretation: Not only is this new aspect of radio communications opening interpretation of natural areas to motorists, but the idea of being able to communicate with hundreds of motorists without having them stop their cars is a patrolman's blessing. Along these lines, the NPS article mentions that the California Department of Transportation had deployed a low-power radio station to advise travelers of a detour on I-5 following the San Fernando earthquake. I have, unfortunately, not been able to find much information about this station---but the NPS article does tell us it used equipment from Info Systems. Info Systems, Inc. appears to have been the first vendor of purpose-built transmitters for low-power informational stations. I haven't been able to find much information about them, and I'm a little unclear on the nature of the company--- they were apparently reselling transmitters built by vendors including ITT. I'm not sure if they were built to Info Systems designs, or if Info Systems was merely a reseller of equipment originally intended for some other application. Of course, I'm not sure what that application would have been, because at the time no such radio service existed. These transmitters operated either at milliwatt power levels under Part 15 rules, or at 10w under experimental licenses. This perhaps explains why the National Park Service figures so prominently into the history of low-power radio: as a federal agency, they presumably obtained their authorization to use radio equipment from the NTIA, not the FCC. The NTIA was likely more willing (or at least faster) to issue these experimental licenses. Info Systems transmitters were extensively installed by NPS, likely over a dozen just at Yellowstone. In 1970, the general manager of Los Angeles International Airport became frustrated with the traffic jams at the arrival and departure lanes. He hoped to find a way to communicate with approaching drivers to better direct them---a project for which he hired William Halstead. Halstead partnered with radio consultant Richard Burden to design and install the system, and we are fortunate that Burden wrote a history of the project. In 1972, a leaky cable antenna was buried along the median of Century Boulevard as it approached the airport. A second antenna was buried along the main airport loop, and two different NAB cartridge message repeaters (tape loop players) drove two separate transmitters. Drivers would thus begin to hear a different message as they crossed the overpass at Sepulveda Boulevard. Here, the short range of the low-power transmitters and inefficient antennas became an advantage, enabling a fairly small transition area between the two signals that would otherwise interfere. Each of the message repeaters had three different cartridges they rotated through: a list of airlines using each terminal, parking information, and traffic information. Some of these recordings, like the traffic information, had different prerecorded variations that could be used depending on the weather and traffic conditions. An interesting detail of the LAX radio system is that it was coupled to a new signage strategy. During development of the recordings, Burden realized that it was very difficult to direct drivers to terminals, since the terminal numbers were indicated by high-up signs that weren't noticeable from road level. Brand new signs were installed that were color coded (to identify terminals or parking areas) and bore large terminal numbers and a list of airlines served. The signs from this project were apparently in use at LAX at least until 2012. There is, of course, a lesson here, in that any new interpretive or information system will be most effective when it's installed as part of a larger, holistic strategy. LAX's new traffic radio station operated at 830 kHz under an experimental license. Unfortunately, early experience with the system showed that drivers had a hard time tuning to 830 kHz using the slider-type tuners of the era, creating a dangerous wave of distraction as they passed the signs advertising the new radio station. Burden wanted to move the station to an extreme end of the AM band, where drivers could just push the slider until it stopped. Unfortunately, 540 kHz, the bottom of the established AM band, was licensed to a Mexican clear-channel station and could not be allocated so near to the border. Instead, Burden convinced the FCC to allow an experimental license for 530 kHz: the vast majority of cars, they found, would receive 530 kHz just fine when tuned to the bottom of their range. The frequency was formally allocated for aviation NDBs, but not in use at LAX or almost any other airport. Thus we have the origin of 530 kHz as one of the two standard frequencies for TIS [1]. By 1973, the FCC had started the rulemaking process to create a 10w TIS radio service. The National Park Service, apparently wanting to take a conservative approach to equipment purchasing, chose to stop buying new low-power AM transmitters until transmitters certified under the new FCC rules were available. In practice, this would take four years, during which time the lost sales to NPS were so great that Info Systems went out of business. During this period, a company called Audio-Sine continued to manufacture and promote Part 15 AM transmitters---but for a different application. The "talking billboard," they proposed, would improve outdoor advertising by allowing travelers to tune their radio for more information on a product they saw along the roadside. The talking billboard concept never really caught on---a prototype, in Minneapolis, advertised for the idea of the talking billboard itself. "Look for talking billboards throughout this area in the near future." At least one other was installed, but in Duluth, advertising for Dean Nyquist's primary race for Minnesota Attorney General. "The Audio Sign... gives a very positive pitch for the City of Duluth..." the campaign manager said. "I would advise the city or chamber of commerce to use one or more all the time." I wonder if he was invested in Audio-Sine. A newspaper article a few days later comments that the talking billboard apparently did not work, something the same campaign manager attributed to a railroad trestle blocking the signal. This is an obvious limitation of Part 15 AM transmitters: the power limit is very low. Audio-Sine only really claimed a range of "4-8 blocks," and today I think you would struggle to meet even that. The more powerful 10W stations, operated under experimental licenses, could reach as much as eight miles in good conditions. Despite their limitations, the Audio-Sine milliwatt transmitters did find some use as early equivalents of TIS. This overlap does make it amusing that when the California Department of Transportation introduced their first changeable message signs around the same time, they called them "talking billboards" in the press. There exists to this day a "microbroadcasting" hobby, of individuals who operate low-power FM and AM transmitters under Part 15 rules. To these hobbyists, who are always looking to transmit the best signal they can within the rules, the specific technical details of these early transmitters are of great interest. They remain, to this day, just about the state of the art in intentional broadcast radio transmission within Part 15 rules. In fact, the availability of these commercially-manufactured low-power AM transmitters seems to have lead to a short-lived boom of "whip and mast" Part 15 AM stations that attracted the attention of the FCC---not in a good way. Various details of our contemporary Part 15, such as the 3-meter antenna, feed line, and ground lead limitation of 47 CFR 15.219, seem to have been written to limit the range of the early 1970s Info Systems and Audio-Sine transmitters, along with a few other less prominent manufacturers of the day. There are historical questions here that are very difficult to answer, which is frustrating. The exact interpretation of the limits on Part 15 intentional radiators are of great interest to hobbyists in the pirate-radio-adjacent space of legal unlicensed broadcasting, but the rules can be surprisingly confusing. You can imagine this leads to a lot of squinting at the CFRs, the history, and what exactly the FCC intended the rules to be when they were originally written. The fact that the FCC actually enforces according to a booklet of standards that it won't release but may be based on 1970s installation practices only makes the matter more intriguing. In 1977, the FCC promulgated Part 90 rules formally establishing the Traveler's Information Station/Highway Advisory Radio service. TIS were allocated 530 kHz and 1610kHz, the two extremes of the American AM broadcast band at the time. Incidentally, the AM broadcast band would later be extended up to 1700kHz, but TIS on 1610 has not been moved. 530 and 1610 remain de facto exclusively allocated to TIS today. TIS rules remain largely unchanged today, although there have been some revisions to clarify that the established practice of "ribbons" (sequences of TIS transmitters) was permissible and to allow 5 kHz of audio bandwidth rather than the former 3 kHz. Part 90-certified TIS transmitters are now commercially available from several manufacturers, and widely installed. Power is limited primarily in terms of field strength, although there is an RF output power limit as well. Leaky cable systems are permitted up to 50 watts into a 3 km long antenna to produce a field of 2 mV/m at 60 m from the antenna; conventional antenna stations are limited to 10 watts power into a vertically polarized antenna up to 15 m high and a field strength of 2 mV/m at 1.5 km. Most TIS installations are "whip and mast" types similar to those at the genesis of the category, using a monopole antenna mounted at the top of a signpost-type mast with the transmitter in a weathertight enclosure mounted to the side of the mast. You learn to recognize them. Typical coverage for a TIS station is 3 km (indeed, that is the limit on the planned coverage area). Searching for TIS licenses is a little odd because of the formalities of the licensing. All TIS licenses must be issued to "government entities or park districts," in part because TIS is technically part of the public safety pool. The AM frequencies allocated to TIS stations are sort of "transferred" to the public safety pool (on a primary basis for 530 kHz and secondary basis for 1600-1700 kHz). In other words, TIS licenses are best found in ULS by searching the PW (public safety pool, conventional) service for frequencies between 0.530-1.700 MHz. There are 1,218 such licenses active. I'm not going to provide a breakdown on all thousand-plus licenses, but I did take a quick look for any "interesting" entries, and some boring ones as examples of a typical application. Consider the very first result, KMH441, licensed to the State of Illinois for 1610 kHz. It appears to have a surprisingly large tophat antenna. It probably serves weather advisories for the nearby freeway. Rather dull, but most TIS are just like this, except with less impressive antennas. KNIP553 is licensed to the Foothill-De Anza Community College District Police in Los Altos Hills, CA, at 1610 kHz as well. It's probably on the roof of one of the campus buildings. Like most TIS, there are essentially no mentions of this station on the internet, except in listings of TIS based on licenses. KNNN871 1610 kHz is licensed to the city of Vail, Colorado, and this one got a local news article when it was installed. There are two transmitters. WNKG901, Greater New Orleans Expressway Commission, is on 1700 kHz and has four licensed transmitters at various toll plazas. The transmitters are standard whips on masts, but this one is in an unusual place. WNRO290, State of New Mexico, operates at 530 kHz at the St. Francis/I-25 interchange in Santa Fe. The transmitter is totally typical and shoved into a median space. WPEZ840 is assigned to the Lower Colorado River Authority and covers 1610 or 1670 kHz at six locations, each a power plant (some of them hydroelectric, but the Lower Colorado River Authority apparently operates some coal plants). Like many emergency-oriented TIS, these stations normally rebroadcast NOAA All-Hazards Weather Radio. While TIS are limited to government agencies, there are definitely some cases of private organizations finding a government sponsor to obtain a TIS license. For example, Meteor Crater in Arizona has signs at the freeway advising that there is attraction information on 1610 kHz. This is WQDF361, which is actually licensed to the nearby City of Winslow. Like many TIS stations, the license contact is Information Station Specialists, a company that specializes in TIS including both equipment and licensing. Because TIS are ubiquitous low-power AM stations, some DX (long-distance receiving) enthusiasts will try to pick up very distant TIS. Historically, some TIS operators would issue QSL cards. Considering that there are quite a few TIS in service that are government-registered but seem to be physically maintained by radio clubs or amateur radio operators, there are probably still a fair number out there that will return a QSL card if you try. Having discussed TIS, we finally need to consider the fact that there are a lot of things that look and feel like TIS but are not. Most notably, when the Low Power FM (LPFM) class was established in 2000, one of the authorized functions of LPFM stations is something that is very much like, but not quite, TIS. A notable advantage of LPFM stations for this purpose (besides the higher popularity of FM radio despite its poorer range) is that the license class explicitly allows large-area networks composed of many low-power transmitters---something that is kind-of-sort-of possible with TIS using very long "ribbon" sequences, but not encouraged. These rules mean that TIS-type LPFM networks can feasibly cover multiple towns. A major example is in Colorado, where the state operates eleven LPFM stations such as KASP-LP, 107.9 FM Aspen. Anyone familiar with the extreme difficulty of actually getting LPFM licenses will be rather jealous of the State of Colorado for bagging eleven, but then government agencies do get preference. The Colorado stations rebroadcast NOAA All-Hazards Weather Radio with 100 W of power, mostly just allowing people to listen to them without having a tuner capable of covering the 160MHz weather band (an unfortunately common problem). It's hard to know what the future holds for TIS. The broad decline in AM radio suggests that TIS may fade away as well, although it appears that AM receivers will be mandated in vehicles sold in the US. Some states, such as Virginia, have significantly reduced the number of TIS in operation. Still, some TIS systems are popular enough with drivers that plans to eliminate them lead to public objections. Most TIS operators are increasingly focusing on emergency communications rather than traffic advisories, since TIS offers a very reliable option for communications that is completely under local control---very local control, considering the short range. [1] Wikipedia suggests that an NDB on 529 kHz at Manchester, TN can be heard in many parts of the US. There's a weird lack of basic information on this NDB, such as its location or the name of the airport it is located at. It seems to have been installed at a private airport by an amateur radio operator, probably as more of a hobby project than anything. I cannot find it on contemporary charts or even find an airport that fits the description, and I don't see references to it newer than 2009, so I think at least the NDB and possibly the entire airport are gone to history.

At the very core of telephone history, there is the telephone operator. For a lot of people, the vague understanding that an operator used to be involved is the main thing they know about historic telephony. Of course, telephone historians, as a group, tend to be much more inclined towards machinery than people. This shows: websites with information on, say, TD-2, seldom tell you much about the operators as people. Fortunately, telephone operators have merited more than just a bit of discussion in the social sciences. It was a major field of employment, many ideas in management were tested out in the telephone companies, and moreover, telephone operators were women. It wasn't always that way. The first central exchange telephone system, where you would meaningfully "place a call" to a specific person, arose in 1877. It was the invention not of Bell, but of Edwin Holmes, a burglar alarm entrepreneur. His experience with wiring burglar alarms back to central stations for monitoring may have made the idea of a similarly-wired telephone exchange more obvious to Holmes than to those in other industries. Holmes initially staffed his telephone exchange the same way he had staffed his alarm and telegraph businesses: with boys. The disposition of these young and somewhat unruly staff members became problematic when they spoke direct with customers, though, so Holmes tried something else. He hired Emma Nutt, the first female telephone operator. Women telephone operators were a hit. Holmes quickly hired more and customers responded positively. The matter probably had little to do with their gender, but rather with the cultural norms expected of young men and young women at the time, but it takes a certain perspective to differentiate the two (for example, it cannot be ignored that the switch from boys to women as telephone operators also involved the other change implied by the terms: most women telephone operators were hired as young adults, not at 12 or 13 as telegraph boys often were). The way the decision was reported at the time, and sometimes still today, is simply that women were better for the job: calmer, more friendly, more professional, more obedient. With her extreme youth, her gentle voice, musical as the woodsy voices of a summer day, her always friendly way of answering calls, she is a sensible little thing, tranquilly serene through all the round of jollies, kicks and nerve-racking experiences which are the result of a day's labor. She likes her place, she knows her work, and she is prepared with quick-witted, instinctive readiness for every emergency which comes her way. [1] Alexander Graham Bell was very much aware of the goings-on at Holmes' company, which AT&T would purchase in 1905. So the Holmes Telephone Despatch Co., the first telephone exchange, became the pattern for many to follow. During the last decades of the 19th century, the concept of exchange telephone service rapidly spread, as did the role of the operator. Virtually all of these new telephone workers were women, building a gender divide in the telephone industry that would persist for as long as the operator. Operators stood out not just for being women, but also for their constant direct interaction with customers. To a telephone user, the operator was part of the machine. The operator's diminished humanity was not unintentional. The early telephone industry was obsessed with the appearance of order and reliability. The role of fallible humans in such a core part of the system would undermine that appearance, and with the social mores of the time, the use of women would do so even more. The telephone companies were quick to emphasize to customers that operators were precisely trained, tightly managed, and a model of efficiency. The virtues of telephone operators, as described by the Bell companies, reflect the semi-mechanical nature of their professional identities: a good operator was fast, precise, efficient, reliable. Within the Bell System, new operators attended training schools that taught both the technical skills of telephony (operation of the exchange, basic understanding of telephone technology, et) and the behavior and manner expected from operators. Operators were not expected to bring their personalities to the workplace: they followed a detailed standard practice, and any deviation from it would be seen as inefficiency. In many companies, they were identified by number. There was, of course, a tension underlying the role of the operator: operators were women, chosen for their supposed subservience and then trained to follow an exact procedure. At the same time, operators were women, in the workforce in a time when female employment remained unusual. The job of telephone operator was one of few respectable professions available to women in the late 19th and early 20th centuries, alongside nursing. It seemed to attract the more ambitious and independent-minded women, and modern studies have noted that telephone operators were far more likely to be college-educated heads of households than women in nearly any other field. A full examination of telephone operators, their role in the normalization of working women, the suffrage movement, and etc., would require a much better education in the liberal arts than I have. Still, I plan to write a few articles which will lend some humanity to the telephone industry's first, and most important, switching system: first, I will tell you of a few particularly famous telephone operators. Second, I plan to write on the technical details of the work of operators, which will hopefully bring you to appreciate the unusual and often very demanding career---and the women that took it up. We will begin, then, with one of my favorite telephone operators: Susie Parks. Parks grew up in Kirkland, Washington, at the very turn of the 20th century. After a surprising amount of family relocation for the era, she found herself in Columbus, New Mexico. At age 17, she met a soldier assigned to a nearby camp, and they married. He purchased the town newspaper, and the two of them worked together operating the press. Columbus was a small town, then as well as now, and Parks wore multiple hats: she was also a telephone operator for the Columbus Telephone Company. The Columbus Telephone Company seems to have started as an association around 1914, when the first telephone line was extended from Deming to a series of telephones located along the route and in Columbus itself. An exchange must have been procured by 1915, when Henry Burton moved to Columbus to serve as the young telephone company's full-time manager. Burton purchased land for the construction of a new telephone office and brought on his sister as the first operator. Rural telephone companies were a world apart from the big-city exchanges of the era. Many were staffed only during the day; emergency service was often provided at night by dint of the manager living in a room of the telephone office. Operators at these small exchanges had wide-ranging duties, not just connecting calls but giving out the time, sending help to those experiencing emergencies, and troubleshooting problematic lines. By 1916, Susie Parks sat at a 75-line common battery manual exchange. Unlike the long line multiple boards used at larger exchanges, this one was compact, a single cabinet. When a nearby lumberyard burned in January and the fire damaged the telephone office, Parks stepped in with a handy solution: the telephone exchange was temporarily moved to the newspaper office, where she lived. The temporary relocation of the exchange would prove fortuitous. Unknown to Parks and everyone else, in February or March, Mexican revolutionary Pancho Villa sent spies into Columbus. His army was in a weakened state, traveling between temporary camps in northern Mexico and attempting to gather the supplies to resume their campaign against the Federal forces of President Carranza. The exact reason for Villa's attack on Columbus remains disputed; perhaps they hoped to capture US Army weaponry from the nearby fort or perhaps they intended to destroy an ammunition depot to deter US advance into Mexican territory. We also don't know if Villa directed his spies to locate the communications facilities in Columbus, but it's said that they failed to identify the telephone exchange because of its temporary relocation. The spies were evidently not that good at their jobs anyway, as they significantly under counted the number of US infantry stationed at Columbus. On March 9th, 1916, Villa's army mounted what might be considered the most recent land invasion of the United States [2]. Almost 500 of Villa's men moved into downtown Columbus in the early morning, setting fire to buildings and looting homes. Susie Parks awoke to screams, gunfire, and the glow of a burning town. A day before, her husband had left town for the homestead the two worked. Parks was alone with their baby, and bullets flew through the modest building. At the nearby infantry camp, two machine gun units came together to mount a hasty defense. While much more formidable than Villa had believed, they were nonetheless outnumbered and caught off guard, some of them barefoot as they advanced towards town with a few M1909s. Susie Parks was barefoot, too, as gunfire shattered a window of the newspaper office. Keeping her head down, she maneuvered in the dark, knowing that a light would no doubt attract the attention of the raiders. Parks found her way to the exchange and, cord in hand, tried their few long distance leads. El Paso was no good: Villa's forces had cut the line. The line to the north, though, to Deming, had escaped damage. The Deming operator must have had her own fright as Parks described the violence around her. In short order, the message was passed to Captain A. W. Brock of the National Guard. Somewhere along the way, a bullet or at least a fragment hit her in the throat. Unsure if she would survive, she hid her baby under the bed. According to most accounts, she stayed with the switchboard, keeping a low profile until the battle ended. According to her son, in an obituary, she took up a rifle of her own and made way for the Army camp. I suspect there are elements of the truth in both: she probably did get a gun, but I think she was more intending to defend the baby than the soldiers, who were apparently able to take care of themselves. The Battle of Columbus ended as quickly as it began, and the exact order of events is told in different ways. Villa may have already given the order to retreat, seeing his substantial losses against the increasingly organized machine gunners from the Columbus camp. In a version more complimentary to our hero, it was the arrival of Brock's company, spotted coming into town, that lead to the withdrawal. In any case, the sunrise appearance of the National Guard in Columbus decisively ended the invasion. It began a series of campaigns against Villa, culminating in the assignment of General John Pershing to oversee a six-month "Punitive Expedition." They didn't find Villa, but they did prove out the use of air support and truck transport for a wide-ranging expedition through northern Mexico. The experience gathered in the expedition would be invaluable in the First World War soon to follow. Susie Parks is remembered as a hero. Charlotte Prince, a former first lady of the New Mexico Territory, and the Daughters of the American Revolution presented her with a gold watch and silverware set at a celebration in Columbus's small theater. General Pershing, on his arrival to begin the Punitive Campaign, paid her a visit to commend her for keeping her post through a raging battle [3]. The original Columbus telephone exchange, and other memorabilia of the Columbus Telephone Company and Susie Parks, are on display in the top floor of the Telephone Pioneer Museum of New Mexico. Parks had set a high standard for her fellow telephone operators, not just in New Mexico but beyond. The next year, the United States would enter the First World War. Major General Fred Funston, an accomplished military leader and veteran of the Spanish-American War, was favored to lead the US Army into Europe. By bad luck, he died of a heart attack just a couple of months before the declaration of war. Funston was replaced by the General he had sent into Mexico. John Pershing traveled to France as commander of the American Expeditionary Forces. Upon Pershing's arrival, he found Europe in disarray. Communications in France were tremendously more difficult than the high standard the Army maintained at home. There were both technical and organizational challenges: telephone lines and exchanges had been damaged by fighting, and the Army Signal Corps lacked the personnel to improve service. The idea to dispatch American telephone operators to Europe likely originated in the Army Signal Corps and AT&T, with whom they already maintained a close relationship. But I like to think that Pershing remembered the bravery of Susie Parks when he signed on to the plan, cabling the US to send send "a force of Woman telephone operators." At the time, women had been admitted to the military only as nurses, and those nurses were kept far from the front. There was substantial doubt about the fortitude of these women, especially as they would be called on to staff exchanges near combat. The Secretary of War allowed the plan to go forward only on the condition that men would be hired preferentially and women would be carefully selected and closely supervised. Operators were selected in by the Army Signal Corps in cooperation with AT&T. It was initially thought that they would be found among the staff of the many Bell operating companies, but the practicalities of the AEF (which was headquartered and primarily fought in France in collaboration with French units) required that operators speak both French and English fluently. There were few French-speaking telephone operators, so AT&T expanded their search, hiring women with no telephone experience as long as they were fluent in French and passed AT&T's standardized testing process for telephone proficiency. These recruits were sent to the Bell System's operator training schools, and all selectees attended the Army Signal Corps' training center at what is now Fort Meade. The first unit of the Signal Corps Female Telephone Operators Unit [4] consisted of 33 operators under the leadership of Chief Operator Grace Banker, who had learned French at Barnard College before finding work at AT&T as an instructor in an operator training school. Their 1918 journey to France was a long and difficult one, as transport ships were in short supply early in the war and subject to German attack. The ferry crossing of the English Channel, not a long voyage by any means, turned into a 48-hour ordeal as the ship was stuck in dense fog in a vulnerable position. Despite the cold and damp conditions, the operators waited two days on deck in preparation to take to the life boats if necessary. Two men on the ship died; at one point French forces mistook its faint outline for an attacker and surrounded it. As Banker would tell the story later, her operators were in good spirits. Their cheerful disposition in the face of the harsh journey served as good preparation for the conditions the operators faced in the field. There was hardly a barracks or telephone exchange for the women that wasn't plagued by leaks, rats, fleas, or disarray as the AEF scrambled to find facilities for their use. The simple mechanics of the telephone system required that exchanges be located fairly close to concentrations of command staff and, thus, fairly close to the fighting. The operators were constantly in motion, moving from camp to camp, and ever closer to the front. Banker's first unit of 33 women quickly proved themselves invaluable, providing faster and more reliable telephone service as they leveraged their French to handle all allied traffic and developed directories and route guides to keep up with the rapid work of the Signal Corps' men in building out new telephone lines. The Female Telephone Operators had proven themselves, and Pershing called for more. A few months later, hundreds more were in France or on their way. Despite the War Department's concern about the willingness of women to work in wartime conditions, telephone operators turned out to be as ready to fight as anyone: when AT&T solicited applications from among the Bell companies, they were swamped by thousands of postcard forms. While some sectors the military were clear that the women operators were brought to Europe for their technical proficiency, there remained a clear resistance to recognition of their work as part of the military art. "Even telephone operators were persistently told that their presence and their girlish American voices would benefit the war effort by comforting home-sick soldiers and lifting their morale" [5]. The operators were, at times, regarded in the same stead as the women "morale volunteers" fielded by organizations like the YWCA. The military was so quick to categorize them as such that, shortly after their arrival, the YWCA was made responsible for their care. Operators were accompanied by YWCA chaperones, furnished to protect their moral virtues from the soldiers they worked alongside. Despite their long shifts at the exchanges, the YWCA expected them to attend military dances and keep up appearances at social functions. Many of the women associated with the AEF, telephone operators and nurses alike, took to cutting their hair short---no doubt a practical decision given the poor housing and inconsistent access to washrooms, but one that generated complaints from the Army and the YWCA. In September of 1918, the AEF and French troops---a quarter million men in all---took on their first great offensive. The logistics of supporting and organizing such a large fighting force proved formidable, and the Signal Corps relied on the telephone to coordinate a coherent assault. The thunder of artillery was heard over the chatter of telephone calls. For the duration of the offensive, a system of field phones and hastily laid long-distance connections, known as the "fighting lines," fell under the control of Grace Banker and five operators she hand-picked to move up to the front with her. They donned helmets and coats, toted gas masks, and took up their positions at temporary exchanges, some of them in trenches. Infantry orders, emergency calls for supply, and even artillery fire control passed through their plugboards as the allies took Saint-Mihiel. As a reward, they moved forward once again, taking up a new "telephone office" at the allied advance headquarters in Bar-le-Duc. There, they camped in old French army buildings and weathered German bombing as they provided 24/7 telephone service for the Meuse-Argonne offensive. Military service was demanding, but still subject to the "scientific management" trend of the time and the particular doctrine of the Bell System. Their long shifts were carefully supervised, subject to performance evaluations and numerical scoring. There was a certain subtext that the women operators had to perform better than the Signal Corps' men who they had replaced. Fighting ended in November of 1918, although many of the operators were assigned to various post-war duties in Europe (including Grace Banker's assignment to the French residence of President Wilson) during 1919. The first 33 operators had spent 20 months in France before they returned to the United States, where Banker would complain of the low stakes of civilian work. After the war, the Female Telephone Operators received numerous commendations. Major General H. L. Rogers of the Signal Corps spoke of their efficiency and the quality of the telephone service under their watch. The Chief Signal Officer reported that "a large part of the success of the communications of this Army is due to... a competent staff of women operators." Pershing personally signed letters of commendation to a number of the operators, referring to their "exceptionally meritorious and conspicuous services." Operators who had worked near the front received ribbons and clasps for their involvement in the offensives. Grace Banker, for her own part, was awarded the Army's Distinguished Service Medal. Of 16,000 officers of the Signal Corps in the First World War, only 18 received such an honor. Considering the decorations these women wore on their Signal Corps jackets as they returned to the United States, it is no wonder that modern accounts often style them as the "first women soldiers." The female nurses of the Red Cross, while far more numerous, were never as close to the front or as involved in combat operations as the operators. The operators were unique in the extent to which they considered themselves---and they were often seen by others---to be members of the Army. After the war, they would learn at the same time as many of their commanding officers they were not. Earlier, the Army had quietly determined them to be contracted civilian employees. None other than General Pershing himself had ordered them to be inducted into to the army in his original letter to headquarters, and recruiting materials explicitly used the terms "enlistment" and "regular Army," even introducing the term "women soldiers." But even before the first 33 shipped out for France, Army legal counsel had determined that military code prohibited the involvement of women. None of the women were told; instead, they were issued uniforms. 450 members of the Female Telephone Operators Unit worked 12-hour shifts, handling 150,000 telephone calls per day, often not only making connections but serving as interpreters between French and American officers. The Signal Corps' male telephone operators, more experienced in the Army, were of such noticeably poorer performance that they were restricted to night shifts---and even then, only in safe territory well behind the front. Two operators, Corah Bartlett and Inez Crittenden, died in the service of the United States and were buried in France with military honors. Years later, it was noted that because of their critical role in military logistics, the operators were among the first Americans to reach the combat theater and among the last to leave. They were discharged as civilians---or rather, they were not discharged at all. Because of the Army's legal determination, the women received no Army papers and were deemed ineligible for veteran's benefits or even to receive the Victory Medal which the Signal Corps had promised them. Despite its recognition of their exceptional service, the military was slow to admit women's role outside of wartime exigency, or even in it. The United States as a whole was even slower to recognize the work of the telephone operators. Despite the introduction of 24 bills to congress, starting in 1927, it was not until 1977 that the operators were declared regular members of the Army and granted military benefits. By the time the act was put into effect in 1979, only 33 operators lived to receive their discharge papers and the Victory Medal. AEF telephone operator Olive Shaw, who tirelessly lobbied for military recognition of her fellow women, was the first burial at the new Massachusetts National Cemetery in 1980. Her wartime uniform, fitted as always with the brass devices of the Signal Corps and the letters "U.S.," was presented to congress as evidence of their rightful role as veterans in 1977 and cited again, in 2024, when all of the members of the Army Signal Corps Female Telephone Operators Unit were awarded the Congressional Gold Medal. It is now on display at the National World War I Museum in Kansas City. The Female Telephone Operators Unit laid the groundwork for the induction of women during World War II---the Women's Army Auxiliary Corps and the United States Navy's Women's Reserve, or WAVES, which is remembered today for its exceptional contributions in the fields of cryptography and computer science. It is fitting, of course, that the achievements of the WAVES would be exemplified by another Grace, Rear Admiral Grace Hopper. "Women's work," far from being frivolous, was now defined as essential to the war effort, and the U.S. military found itself in the uncomfortable position of being dependent on female labor to meet the structural needs of the war economy. Ironically, then, it was the logic of sex segregation in the civilian economy that compelled the U.S. government to grant women entry into the armed services, the ultimate masculine preserve. [5] [1] "A Study of the Telephone Girl," Telephony magazine (1905). [2] A 1918 conflict at Nogales, AZ, involving similar combatants, might also lay claim to that description. I will argue in favor of the Battle of Columbus, which was an unprovoked invasion, as compared to the Battle of Ambos Nogales which was more of a border security conflict in reaction to years of rising tensions. [3] Parks was an interesting figure for the rest of her life. She and her husband continued to move around, buying the Clackamas News in Oregon. Her husband's condition declined, a result of surgical complications and a morphine addiction, and they split up. During the Second World War, Parks found herself back in wartime service, as a sheet metal worker at the Seattle-Tacoma Shipbuilding Company. In 1981, the Deming Headlight, closest newspaper to Columbus, reprinted her obituary from the Seattle Post-Intelligencer. It recounts a half dozen careers, two husbands, and 36 grandchildren. [4] The members of the Female Telephone Operators Unit are frequently referred to as the "hello girls," but this is a more generic term for telephone operators that would also come to refer to other groups, be used as the title of works about telephone operators, etc. I prefer to stick to something a little more precise. [5] Susan Zeiger, "In Uncle Sam's Service: Women Workers with the American Expeditionary Force, 1917-1919" (2019).