OVERALL VIEW OF THE 307X0 CAREER FIELD
If the base operator could not establish contact with the phone operator at a distant base, the “go to” shop to get a problem fixed was tech control. Mind you, tech control didn’t actually “fix” anything at the TCF, they used the patch panels to identify the location and possibly type of equipment that was defective, and issued a work order to the appropriate maintenance shop to actually get the work done. At TSN, the Army’s Integrated Wideband Communications Stations (IWCS) did most of the work on voice circuits.
The tools the controllers used on this job were racks of test equipment such as oscilloscopes, signal generators, voltage and decibel meters, as well as various types of analyzers. If the problem was with nearby equipment or lines, the controller would call the associated maintenance shop on base. If the problem seemed to be off base, the controller would pass on the problem description to the next TCF up the line. This was accomplished through the use of a high-priority voice or teletype orderwire connection used only by tech control. These orderwires normally possesed the highest priority of any channel on a given trunk, because they were needed to restore the trunk itself should it become unusable. The technique often used to restore a trunk would involve placing the orderwire circuit temporarily on an alternate routing, sometimes thousands of miles removed from its normal path.
Individual TTY circuits were combined together by multiplexing, and this process resulted in what was called a tone group, which to the uninitiated, sounded like the angry buzzing of a Hornet's nest. As stated earlier, a single such tone group would occupy one voice channel. The voice channels in turn were multiplexed into subgroups and supergroups, some of which had the potential of handling thousands of voice circuits simultaneously for in-theatre transmission. These multiplexing techniques were known as Frequency Division Mux (FDM), which has today given way largely to Time Division Mux (TDM). For longer distances, such as spanning an ocean, a tone group might travel by submarine cable, or it might be placed on a high-frequency radio system. Many tone groups could be found on these short wave frequencies well into the 1970s. The multiplexing equipment used on the high frequency trunks was often more complicated than that devoted to other transmission types because for reliability purposes it needed additional diversity circuitry to overcome the common effects of radio path fading.
If there was a problem with a given TTY trunk, such as a shortwave broadcaster illegally using a frequency assigned to a TTY trunk (not that unusual) this meant the trunk would have to be routed on alternate path until the original problem was cleared up. This "alt-routing" as we called it, was often accomplished by preempting the lower priority channels that occupied the alternative trunk if there were not sufficient spare channels available. Interoperability for these communications circuits was excellent, and a troubled Air Force trunk could be alternatively routed over systems operated by any other branch of the military or naval services. This was possible because the Tech Control facilities were standardized under the Defense Communications Agency (DCA), and inter-service cooperation was a daily event. At this time the Army, Navy, and Marines had TCFs operated by dedicated tech control personnel. Bandwidth was a guarded resource, and it was parceled out to the user with the highest authority and greatest need. At TSN most work of this nature was done by IWCS, which I believe was run by the Army’s 69th Signal Bn.
MY BACKGROUND AS A TECH CONTROLLER
QUALIFYING FOR TECH CONTROL DUTY IN VIETNAM
GETTING THERE AND SETTLING IN
USAF TECH CONTROL AT TAN SON NHUT
Speaking of new technology, it was at PAFCO in 1969 that I saw my first electronic “memory”, a device that appended four-letter station identifiers to the TTY messages. Most of the TTY circuits ran at less than 75 bits per second, the speed at which unencrypted channels operated for a throughput of 100 words per minute (WPM). The crypto equipment used in those days required a lot of support, which accounted for perhaps 20% of the tech controller’s time on the job. About 15 years later, we would learn that the notorious Walker family had compromised much of the military communications security (COMSEC) of the Viet Nam era for small payments from the Russians. My feelings about these traitors are strong.
The third location for USAF tech controllers was at 7th Air Force Headquarters. This facility had its own TTY torn tape communications center, which if I remember correctly primarily handled MACV traffic. A single 5-level controller manned the tech control position at HQ. There was no need for the tech control NCOIC to sleep here, but he did. Nightly he could be seen behind the panels on the floor, without benefit of blankets or pillow. Apparently the security of the steel reinforcement around the bottom floor of this building is what caused him to endure the visible sores and discomfort.
Through this TCF passed the “Red Rocket” TTY messages which were “heads up” for the overflight of the SR-71 Blackbird. I recall a series of messages at 7th AF HQ that originated in South Vietnam, and may have gone as far as Washington. They were about an unfortunate Vietnamese farmer who had been killed by a phone pole that fell loose from the sling of a helicopter. Much of the message series had to do with determining the worth of this hapless soul, with a lot of deliberation being based on how many animals he owned.
If the Vietnam War was micro-managed, much of this was accomplished through HQ 7th AF via TTY messages. I recall countless frag orders that were sent to Washington for review. All the details of upcoming airstrikes were contained in these sensitive messages that went back and forth halfway around the world over what may have been a compromised communications system. How many American lives were lost because of this? Perhaps my feelings towards the Walker family can be better understood in this light.
A fourth Tech Control location opened up late in my tour in the Pulsed Integrated Automated Communications System (PIACS or PIAACS). I think this was not far from PAFCO, and as I recall, the PIAACS scheme was a very large and complex one. All sorts of equipment bays, fresh from the states, were wired up at a half dozen places in Vietnam for this system. Lots of programming was involved, and I recall volunteers being used to wire up little matrix boards. The purpose of this system may have had something to do with real-time bomb damage assessment. It was still in the construction phase when I left for “the world.”
A typical shift at the various USAF TCFs at TSN had one 7-level and three 5-level USAF tech controllers on duty working the circuits over which moved many hundreds of TTY messages per hour. I think the Air Force had perhaps 250 dedicated TTY circuits that terminated at TSN, and there may have been a similar amount for the Army. Surely the Army handled hundreds if not thousands more “through circuits”, those which did not terminate at TSN, but went on to other SEA bases. In addition to the people mentioned above, there were several other 7-levels and at least the one 9-level at the AGL administrative office during the day shift, and two PIACS 5-levels. The traffic load for TSN was immense and unrelenting. It was a huge 24/7 operation.
DESCRIPTION OF 15 MINUTES ON SHIFT AT AGL TECH CONTROL
º Customer at TSN calls AGL on the phone reporting his TTY circuit XX59 is unreadable. He knows this because there is random “garbage” printing on his roll of paper.
º AGL controller uses a patch cord to plug in his “monitor” printer, and verifies it is unreadable, while calling out to the crew, “we lost XX59.”
º AGL controller calls the Army IWCS tech control and advises them XX59 is out of service. At the same time, he plugs in a “distortion analyzer” to see if there is a pattern to the problem, which would be visible on the instruments screen. No pattern is seen, just garbage.
º IWCS calls back a few minutes later advising a certain high-frequency radio trunk had been lost between Clark AFB and McClellan. Reason unknown at this time. XX59 had been down for six minutes at this point.
º Customer on XX59 had called his boss, and AGL tech controller is now hearing from a Major about the need to have “his” circuit back in service quickly. “Working on it, sir” say the AGL controller, with a couple of other comments on the side when the push-to-talk button is not pushed. The Major didn't know it, but XX59 only had a restoration priority (RP) of 2 Alpha, and the controller was previously attempting to restore several much higher priority circuits that if not back in service NOW, would create great concern several levels up the chain of command.
º AGL phone rings again, it’s the tech controller at PAFCO relay, and they lost contact with Hickam AFB on all four circuits. Though the problem with XX59 is fading in importance, it is now eight minutes since it went down. In two more minutes a report needs to be written and a message sent to the Defense Communications Agency reporting the loss of XX59.
º AGL phone rings again. TTY maintenance wants AGL controller to patch over a piece of gear so he can perform scheduled preventative maintenance (PM) on it. “Gimme a minute-real busy right now”, says the AGL controller. “Yeah, sure, I’ve seen you guys on the night shift before, I know how busy you are” says the TTY maintenance troop jokingly.
º PAFCO calls, advising all Hickam circuits are back in service. Though no report to DCA will be necessary, it can take PAFCO hours to recover from this interruption, because the lost messages will need to be retransmitted via the slow, overloaded TTY circuits.
º Major from XX59 calls again, “What are you guys doing to help me? I need an explanation!” XX59 had been down for 12 minutes now.
º AGL calls the IWCS controller, requests status of trunk over which XX59 is routed. “Gonna be down for along time, microwave system at San Miguel was taken out by a typhoon. But guess what? I got your XX59 on alternate routing and it’s looking good. How come your not passing traffic on it yet, Air Force?”
º AGL controller looks at the analyzer and sees a good signal on XX59. Damn, “I hate it when Army gets the jump on me” he mutters.
º AGL controller calls customer at XX59, advises him circuit is back in, go ahead and resume traffic. Airman at XX59 says, “we got no traffic for it until day shift. No big deal.”
º AGL controller concludes there will be no sweat “fudging” on this one, no lost traffic on a 12-minute outage means no report to DCA necessary. Good deal, he thinks, “ I’ll get to look at the new Playboy magazine.”
º PAFCO calls, “Hickham circuits are down again-get an alternate routing, will ‘ya?” So much for the centerfold. That’s how Tech Control went at Tan Son Nhut, 24/7, for a very long time.
Story and photos © 2007 by Tom Hildreth