Re: History of Hayes Modem

(Snipped much excellent discussion of the early years of our crazy hobby.)

[TELECOM Digest Editor's Note: My question would be, _who_ was the > inventor of the MO(dulate)DEM(modulate) in that case? If Hayes only > 'refined' it somewhat, with 'smart stuff' in it such as 'AT' and '+++' > then whose idea was it to ship data over the phone wire originally? PAT]

Let's not forget about the "Acoustic Coupler" which was sort of an accessory to a modem. I don't remember exactly, but I suspect the heyday of the acoustic coupler was before Tom Carter won the right to connect privately owned equipment to the telephone network in CarterPhone -vs- AT&T.

Anyway, in the days when many computers connected to the telephone network through fixed facilities (also remember the DAA - "Data Access Arrangement" which allowed privately owned modems to be connected to the telephone network) there was sometimes a need for portability. You could get a hand truck and move your terminal equipment from place to place. Maybe you had a Teletype machine or, if you were really modern you had a "glass Teletype" which was a CRT based terminal. But when you got where you were going you needed to make a connection to the service you used. If there were no DAA available ( it needed to be previously ordered from and installed by the telephone company) you were S.O.L. as it were. This is where the Acoustic Coupler entered the picture.

The meat of the acoustic coupler was a pair of "cups" into which you placed the handset of a telephone. One cup had a speaker in it; the other cup had a microphone. The microphone and speaker were connected to the modem portion of the thing (which had an RS-232 connection for your terminal or computer). When a telephone handset was placed in the cups properly the coupler's microphone "heard" the signal coming from the handset's receiver and the coupler's speaker "talked" to the handset's transmitter. So the modem was coupled acoustically to the telephone line. This got around the issue of needing a DAA to make an electrical connection to the telephone network and nearly any telephone would work. So with the modem connected to the Teletype and the acoustic coupler "connected" to the telephone you established a connection and got your work done or browsed through the latest messages on your favotire BBS.

Acoustic Couplers pretty much topped out at 300 bits per second. The first one I used was part of a Teletype network and was a 110bps device (that was slow!). Later I got one of those Texas Instruments thermal printer terminals with an acoustic coupler built in; it would go 300 bps and I could carry it with one hand! I thought nothing would be able to stop me then!

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Al Gillis
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