Saturday, July 30, 2011

Stereo Typing: Radioteletypes Recalled

Many old films about the newspaper business feature a newsroom scene with rhythmically clunking teletypes pounding out yellow reams of copy. The occasional closeup in which dramatic words appear on the paper as if by magic told the viewers nothing about how a teletype machine actually worked. Nor should it have. I have long outgrown the private misconception that most moviegoers were just like me, and would have enjoyed ten-minute disquisitions on the details of any technology featured in a film, while the plot ground to a halt. But one day in my teen years, still under the spell of that delusion, as I perused the remoter regions of a surplus-equipment warehouse I was delighted to find an army-green metal box with a keyboard sticking out the front. Inspection proved the device to be an old Kleinschmidt-brand tape-printing teletype, probably scrounged from a small-town telegraph office two or three decades before (this was about 1975). I probably paid about ten bucks for the thing, and the owner was glad to get it off his hands. It weighed a ton and I could barely get it in the tiny trunk of my VW Beetle, which was noticeably down at the head as I drove home with my prize.

My mother, accustomed to seeing all manner of indescribable junk brought home after my surplus jaunts, was nonplussed at hearing I had procured a teletype machine. “Just don’t get any oil on the carpet,” she said. The thing did have a characteristic smell, composed of equal parts of machine oil and burned carbon brushes. After hoisting it up on the workbench in the garage, I removed the case and pondered my purchase.

Back in the 1920s, teletype machines were as cutting-edge as Kindles or 3-D Nintendos are today. They spelled eventual doom to the old-style hand-copying telegraph operator, who had been the mainstay of the telegraph business since its inception in the 1840s. With a teletype, one skilled typist (typically a woman) could do the work of several hand operators. Plus which, she could type out copy in advance on paper tape for batch transmissions, and the paper tape copy disgorged by the receiving teletype could simply be pasted on a telegram form and delivered, almost untouched by human hands (except at the transmitting end). So by 1950, as Western Union experienced its own “peak message” year and saw its business head for eventual decline, teletype use was nearly universal.

How did a teletype circuit work? As I learned by reading old radio-amateur books, the teletype was simply an automated form of the old make-and-break telegraph key. The original Morse code consisted of dots (short electrical pulses) and dashes (by convention, three times longer than dots) in specific patterns. The teletype used the same idea, only mechanized and synchronized so that once a human being at the transmitting end pressed the key for a given letter, no further human intervention was required.

Suppose the letter pressed was “R”. Here’s what happened next. Pressing any key released a cam follower which opened a switch for a few milliseconds. Then for the next five equal intervals of time, the cam opened and closed the switch in this sequence: open-close-open-close-open. Then the switch closed and stayed that way until the next keystroke. By convention, the presence of current was called “mark” and the absence “space.” All characters began with a single space pulse.

My teletype machine used what was called a “5-bit” code. During each of the five precisely timed intervals, the switch was either open or closed. This allowed the transmission of 25 = 32 unique characters—in other words, the alphabet plus a few more symbols. Numbers had to be sent after the transmission of a special “uppercase” signal that shifted the receiver carriage to uppercase mode.

The same kind of telegraph wires that Morse & Company used carried teletype signals too, at least to the smaller stations. The transmitting equipment consisted of a high-voltage power supply—100 volts or so—with enough series resistance to limit the closed-circuit current to 20 mA. In this way, about the same current flowed through the circuit regardless of the length of line, and all telegraph circuits connecting different stations along a line were in series. In that way, transmissions from one circuit-interrupting station could be received by all the other stations along the line.

At the receiving end, things really got interesting. My teletype was both a transmitter and receiver, which was fortunate, because I would have been hard put to come up with a receiver for a transmit-only unit or vice versa. The transmitted current went through an ordinary relay coil that operated an adjustable armature. As soon as the armature was released following the initial space pulse, a rotating cam began to throw a kind of feeler lever at the armature five times. Each throw corresponded to the most likely time that a mark or space was present. Depending on whether the armature was pulled in (“mark”) or released (“space”), the feeler lever landed on one side or another of the armature. In sequence, this landing on one side or the other shoved five stacked semicircular bars of metal slightly to the left or right of their original positions, before the character was received.

The bars of metal were arranged in a semicircular basket shape rather like an old-fashioned manual typewriter, and rods connected to each of 32 typebars rested against the edges of the semicircular bars. Each semicircular bar had precisely positioned notches cut in it in such a way as to decode the particular character sent by the transmitter. For example, when “R” was received, the bars were pushed left-right-left-right-left, going from top to bottom of the stack. At the end of the character transmission, another mechanism pressed all the typebars against the five semicircular bars. The slots in the semicircular bars were cut so that only one typebar—the “R” bar, in this case—fell outward, because all five of the slots in the five sheets of metal lined up, and none of the other bars had all five slots clear. So for each character, only one of the 32 typebars could clear all five movable slotted bars and get to strike its character. It was rather like a complicated lock mechanism that rearranged itself every time a character was received, and only one key—the correct character typebar—would fit the lock each time. Yet another mechanism used the fact that the “R” bar fell outward to actuate the typebar carrying “R,” and only that typebar, to strike the paper tape. That is, if one had a paper tape to strike.

That was one of my many problems in getting the thing to run. I wasn’t about to sit around with a roll of calculator paper and manually cut a long strip of paper of the right width. After much experimentation, I discovered that ordinary (at least, ordinary back then) quarter-inch reel-to-reel magnetic tape fit through the tape-feed mechanism with only an occasional tape jam. It wasn’t too easy to read the dimly printed characters struck from the worn-out ribbon onto the dark-brown acetate tape, but after a lot of fiddling, I was able to strike a key and get the corresponding letter to print.

I left out a lot of other stuff I had to do first. One reason the machine was so cheap, I discovered after taking it home, was that it had a 110-volt DC motor. That’s right, not AC, but DC. It took me a while to come up with a power supply beefy enough to provide the amp or so that the motor needed.

Then there was the governor, a large disc-shaped thing on one end of the motor shaft that spun around dizzily whenever the motor was powered up. Especially if more than one teletype was involved, you had to ensure that the motor in your machine was turning at exactly the same speed as the other guy’s motor, if the marks and spaces were going to line up properly. With AC motors, this is a simple matter of using a type of motor called “synchronous,” but mine wasn’t that way at all. It had some kind of weird centrifugal switch that would gradually cut in and out as the motor reached the proper speed. I’m not convinced it ever really worked properly. As long as I was transmitting only to myself, it didn’t matter because the same machine was doing the sending and receiving. But when I got more ambitious and decided to try and receive radioteletype signals, things got even more complicated.

Back then, not only did radio amateurs do a fair (non-profit) business in the transmission of what was termed “RTTY” contacts, but there was a great deal of international short-wave news traffic transmitted by radioteletype. The notion of reading that news right off the air fascinated me, and I spent most of a spring vacation during college trying to pick up RTTY transmissions. Such was the life of a truly dedicated nerd in those days.

There were two main problems in the way of my getting the radioteletype signals to print. First, I had no way of measuring what the actual speed of the motor was, so it was a matter of guessing an adjustment and hoping it would have the right effect. Second, and worse, was the RF interference that the DC motor produced. It had brushes that sparked and flashed and smelled like the air after a thunderstorm, and that plus the contacts in the governor trashed most of my attempts at reception of any but the strongest signals. Finally, after many fruitless tries, one afternoon I tuned in a strong commercial RTTY station that I’d gotten familiar with, and was rewarded with the sight of two or three sentences’ worth of genuine pirated news—in Spanish. It was probably some South American regional service.

Having achieved that triumph, I gradually lost interest in the thing. My amateur radio license lay a few years in the future, so I had no way of actually using the thing for two-way communications unless I convinced a friend to buy another teletype and we rigged up a private telegraph line. In suburban Fort Worth in 1975, this was not practical.

The year after I bought the teletype, I flew home from Caltech during the spring break of my sophomore semester. My grandmother (my father’s mother) was very ill with stomach cancer, and we planned a visit to her house the day before I was to fly back to California.

I had spent most of the week trying to get my teletype to work, and had succeeded in getting the Spanish-language news copy just a day or two earlier. In my myopic world, this was the big news, and I am afraid that the teletype might have been the main subject of my conversation to her that day. Then I asked her how she was doing. By her looks, she was doing pretty awful. She was propped up on a pillow in her bed, and when she raised her arms to hug me, her flesh hung limply from her bones.

I do not remember much about what she told me, except for one thing. I do not recall how the subject came up, but she began to talk about the time she visited the 1904 St. Louis World’s Fair, and what a good time she had there. She was probably about eighteen in 1904, about the same age I was at the time we spoke. Maybe that’s why she brought it up. I don’t remember. So the last thing I talked to her about was some old piece of machinery I had managed to get going, to no one’s satisfaction or benefit other than my own. And the last thing she told me about was the time she saw a glittering new vision of a glittering new country in a glittering new century, when she was glittering and new herself.

The next day, my father and I got up early so we could get to Love Field in Dallas in time for my flight. For reasons having to do with packing as much as formality, I always flew in my suit in those days, so I suited up and got in the car. We didn’t say much on the drive over, except that my father talked about how we might handle the eventuality of Big Mother’s death. (That was what all her grandkids called her, in the old Southern tradition.)

We got to the airport and had an hour or so to wait. This was long before terrorist-inspired inspections and metal detectors, so he and I had the run of the place. At one point I had to go to the bathroom. As I stood there taking care of business, I heard the PA announcer page my father for a phone call. That could mean only one thing.

I rushed outside as fast as I could and caught up with him as he was running for a courtesy phone in the middle of the large open two-story lobby or atrium they had back then. Once on the phone, his face looked like he was speaking with a past-due loan customer. He listened a moment and broke in to say, “Is she dead?” She was.

My Aunt Fanny, who lived with Big Mother, had gotten up that morning and found that her sister had died during the night. As she recalled later, she “had her little emotion,” as she put it, then called my mother after we had left for the airport. My mother called the bank, thinking maybe they could get hold of my father faster, and a secretary there had the notion to call the airport. Thus were emergency messages conveyed in the days before cellphones.

Needless to say, I missed the plane and stayed for the funeral. At times during the proceedings, I recalled something that happened the night before she died. My spiritual state at that time might be best described as conservative-agnostic. I knew I was a conservative politically, but as for God and all that, why, I wasn’t sure. But I knew Big Mother was sure there was a God. In the spirit of Pascal’s wager, I had been in the habit of praying a highly ritualistic prayer of my own invention every night before I went to bed. This was just in case God happened to be there, so that at least I would have some prayers to my credit at the great reckoning. (The “Now I lay me” prayer my mother had taught me I had long since discarded as morbid and childish.) But that night, after seeing Big Mother in such pain, I put aside all ritual and asked God, in my mind, either to make her well or take her to Himself. And maybe it is retrospective revision of memory, but I seem to recall a sense that something, or someone, was there listening to my thoughts, and as soon as I finished praying, moved off into the moonlit night. And the very next day, she was gone.

Like most (not all) alleged miracles, this one is susceptible to a number of naturalistic explanations. People can will themselves to live a few more days if a particular event has meaning for them. Perhaps this is why Thomas Jefferson died (or chose to die?) on July 4, 1826. So maybe my grandmother hung on a few more days to see me off to school before she let go. I will never know for sure in this life.

That situation—the answered prayer and the end of a life lived wholly in God’s care despite my blind ignorance of its depths—made an impression on me that never left me. I now believe in the God of my grandmother. If there is any justice in the universe, she is there with Him, and in the communion of saints we will be able to talk again. Only this time, I won’t bring up teletypes. At least, not right away.

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