Does anyone have technical information on Bell 401 datasets, such as the
401H and 401L transmitters, and the 401F and 401J receivers? In particular, I'm interested in what frequencies, signal levels, timing, and tolerances were used.The 401 series used multifrequency signaling, with up to three simultaneous tones out of eleven choices in three bands. Since they were for customer use, I assume that they were chosen to not conflict with in-band MF signaling.
Eric
I believe these are touch-tone decoders which are intended for remote control.
The Technical Reference Catalogue indicates that you want PUB41403, which describes "Data Set 401J is a multi-frequency data receiver intended for use on DATAPHONE service. It can receive either 3-out-of-14 or 2-out-of-8 parallel signals at a speed of up to 20 characters/second." It is dated Sept. 1965.
Dunno, I have only seen them used for touch tone. The Periphonics systems used for touch-tone banking used them for the customer interface.
--scott
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