National Geographic : 1954 Jul
New Miracles of the Telephone Age the millions of picture signals with a minimum of distortion to 63 broadcasting stations scat tered from coast to coast. The operating center in the Long Lines building is television transmission headquar ters for the entire United States. At first impression it seems like a leisurely place. Facing TV screens along one wall sit four men who spend most of the day looking at televi sion-and get paid for doing it. Their job is not as relaxing as it looks, however. These transmission men are not watching programs. They are monitoring pic tures, which is quite a different thing. A Flicker Means Trouble They pay no attention to the plot of the TV drama. But a flicker in the picture, a double image, or a momentary fading sends them into a flurry of activity. Beside each man's screen hangs a telephone. By calling the network control room and monitoring points along the relay system, they usually pinpoint a breakdown within seconds and alert the technicians to fix it. Meanwhile (if the difficulty is in the A. T. & T. facilities), the program is re-routed to another channel. Other spurts of activity come on the hour, the half-hour, and the quarter-hour. Our New York advertiser bought a coast to-coast network for his program. The next sponsor, however, may want only stations along the east coast from Boston to Florida. This means that between the two programs the network must be rearranged. It's done by pushing buttons on a big con trol board in the monitoring room. I watched a transmission man make the switch skill fully, pressing the knobs two at a time. He had just 20 seconds between programs to do it. "Do you ever make a mistake and push the wrong button?" I asked Arthur Dittmeier, the transmission supervisor in charge. "It has happened," he admitted, "but very rarely. When we do make a mistake, it doesn't stay made very long. Usually we catch it here. But if we don't-the station owners monitor their own shows, you know, and when they suddenly find they're getting wrestling matches instead of Marilyn Monroe, they let us know promptly. And I mean promptly!" The program signals move from the moni toring room to the roof of the Long Lines building. Here they are mounted on super high-frequency radio waves and amplified so that they can make the jump to the next relay tower in Martinsville, New Jersey, 25 miles away. The superhigh-frequency (SHF) waves used in microwave relays are a little longer than a man's finger. About four billion of them fly past a given point in a second. They can be focused, like rays from a spotlight, into a sharp, one-directional beam. This is done through a lens in the antenna, developed by Bell Laboratories. The beam can be sent from relay to relay with less than one watt of power. Amplified and modulated, the television pic ture is ready to begin its transcontinental trip. It will leap from tower to tower 106 times on the way. And it will reach San Francisco in about 1/50 of a second after it leaves New York (color diagram, page 96). At each tower the signal is reamplified and its frequency changed again-raised or dropped by 40 million cycles a second. This is to avoid the double images, or "ghosts," that might result if part of the signal beamed at one antenna overshot its mark and reached the next antenna down the line. For the same reason, the relay towers are placed in a slightly zigzagged position. Telephone engineers have taken elaborate precautions to prevent breakdowns in the un attended relay stations. At Mount Rose, for example, Jerry Miller showed me a Diesel powered 40,000-watt generator that turns it self on if power fails. An 8-month supply of Diesel oil is kept on hand. He also showed me a miniature air-cooling system which keeps the station's vacuum tubes from overheating by blowing a jet of air on each individual tube. Alarm System Guards Station Standing guard over all the Mount Rose equipment is an intricate alarm system. If anything goes wrong, it flashes a warning to a telephone exchange in Reno, where a repair crew is always available. The alarm not only reports trouble, but blinks a light in a chart showing specifically what the trouble is whether it is a burnt-out tube, a shortage of Diesel oil, or even if the front door is open! If a microwave channel does fail, the audi ence watching the television program at home usually does not know the difference. In most cases, before the failure becomes noticeable to the human eye a much keener electronic eye has detected it and switched the program to a reserve channel.