The MIT Dormitory Telephone System
MIT Dormphone - II

EQUIPMENT - Battery Chargers

EQUIPMENT - Battery ChargersMy recollection is that Baker had a small wall-mounted charging unit with two tungar rectifier tubes. Ashdown originally had two motor generators. I believe they were 35 amperes each. These were later replaced by a solid state unit. The most interesting charger was the one in Walker (East Campus), shown at left. It was given to us by New England Telephone Company and consisted of three 30-amp units with a common control circuit. Each unit used two tungar tubes, the brightness of which was proportional to current flow. Occasionally the system would go into full charge and light up part of the room with a scary blue glow. More frequently, it would refuse to charge at all, and the Dormphone person's task was to figure out what was wrong before the batteries went flat. I never did figure it out. Frustrated after an hour of examining the circuit diagrams, I would go next door to the radio station and buy a Coke. When I returned, it would be working. After graduation, I worked at Lincoln Lab which had a similar system that had been converted to solid state rectifiers. The control circuitry was the same. One day it failed, and I thought I would finally find out how a professional repairman fixed it. When I dropped by the switchroom several hours later, he reported that he had not found the failure - it had suddenly started working! (By the way, the cartoon posted on the charger shows two men, one of whom is installing a phone. He says, "To me, Lou, it's more than just installing a phone. It's giving one human being the means to reach out to another.")

Next: EQUIPMENT - Switches

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