[GreenKeys] History of modems

[Jack Hart]

A tremendous source for parts....

 

Jack K0TTY

 

 

 

From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Duncan Brown
Sent: Thursday, November 7, 2013 8:46 PM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] History of modems

 

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-mod
ems-657479 

jhhaynes at earthlink dot net 
______________________________________________________________ 





  _____  


 <http://www.avast.com/> 

This email is free from viruses and malware because avast! Antivirus
<http://www.avast.com/>  protection is active. 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20131107/0c09b528/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 154866 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20131107/0c09b528/attachment-0001.jpg>