[Milsurplus] overheard telephone conversations

[mstangelo at comcast.net]

Prior to WW2 the Bell System used single sideband with compandors and VOGAD(voice operated gain adjusting device) processing.

It was not encrypted but you would have to be able to receive sideband and probably use a voice expandor.

There is an excellent writeup in the Bell System Technical Journal Volume 19, Issue 4 (October 1940) starting on page 611.

The Technical Journal were available for Lucent. They are now available from the IEEE.

Sigsaly was not used for commercial voice traffic. I don't know what additional processing was performed after WW2 until 1956 when they started laying underwater coax cables capable of carrying voice. I believe Sigsaly was one of the outstanding electronic accomplishments of the Second World War.

Mike N2MS


----- Original Message -----
From: Kenneth G. Gordon <kgordon2006 at frontier.com>
To: MilSurplus Forum <milsurplus at mailman.qth.net>
Sent: Tue, 31 May 2016 15:59:46 -0000 (UTC)
Subject: Re: [Milsurplus] overheard telephone conversations

On 31 May 2016 at 11:32, Al Klase wrote:

> OK.  It's time to read the SIGSALY article on Wikipedia:  https://en.wikipedia.org/wiki/SIGSALY

Wow! What a complex system! And the article is very interesting. Thank you, Al.

Ken W7EKB