[GreenKeys] History of modems

[Duncan Brown]

It is often hard to pinpoint the "first" of anything, but the for the 
"first" modem, I always think of the US Signal Corps' TH-5/TG:



This was the Signal Corps' first tactical (came with a water-proof 
cover) modem and probably the first mass-produced modem. Not designed 
for civilian telephone lines but used with 2-wire (simplex) or 4-wire 
(full duplex) field-phone circuits. Designed c1950 for 60/100 wpm 
teletypewriter circuits and so operated at 42 & 75 bps/baud. Two-tone 
AFSK: 1275 & 1325 Hz. Uses 15 tubes, mostly 12AU7s & 12AX7s, and weighs 
about 18 pounds. Contains two 20ma loops - one for RX & one for TX. 
Contract date is 1951 & first manual date is 1952.  A solid-state 
version, the TH-22/TG came out about 1967. It was the same size and 
didn't weigh any less. The TH-5 operator's manual was updated in 1983, 
so it was apparently still being used then.

Duncan
K2OEQ
USASA 31J


On 06-Nov-13 12:06, Jim Haynes wrote:
>
> http://www.techradar.com/us/news/internet/getting-connected-a-history-of-modems-657479 
>
>
> jhhaynes at earthlink dot net
> ______________________________________________________________



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