TELECOM Digest OnLine - Sorted: Re: Very Early Modems

Re: Very Early Modems

Jim Haynes (
Sat, 28 May 2005 19:26:03 GMT

One of the problems with the modems circa 1960 was that AT&T felt they
should operate over nearly any dialed-up connection between any two
points. With the state of the telephone plant in the early 1960s this
was a tall order. There is a paper (which I can't readily reference)
where Bell Labs did a bunch of test calls all over the U.S. to assess
the ability of their modems to communicate with acceptably low error
rates. This would be a requirement for TWX, offering nationwide
service, and for higher-speed modems. At higher speeds typically a
corporation would make calls all over the U.S. to collect data from
its local offices.

The makers of acoustic couplers and would-be makers of third-party
modems realized that for the bulk of the market - computer time
sharing terminals -- most connections would be local or nearly so and
they could get by with a much lower-performance modem. Meanwhile the
telephone plant was rapidly improving and the probability of getting
an unusable connection was steadily going down. So the Bell modems
were overdesigned and consequently overpriced for the kind of service
that much of the market needed. --

jhhaynes at earthlink dot net

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