[Milsurplus] Mystery Signal Corps (?) module

[radioman390 at cs.com]

In the early days of mobile telephones av 2605 Hz (oops cycles in those days) tone was generated on the base station voice path while a call was in progress to mark the channel "busy" and acivating a mute circuit in other mobile units to provide a bit of privacy. It was also used for dialing to the mobles by pulse interruption as on rotary dials. 
I was told 2605 was used because the earpieces used in teleohony didn't go that high in audio response, so it could co-exist with voice frequencies (below 2500 cycles).
kd2bxa 

 

 

 

-----Original Message-----
From: Peter Gottlieb <kb2vtl at gmail.com>
To: Nick England <navy.radio at gmail.com>
Cc: Military Surplus Mail List <milsurplus at mailman.qth.net>
Sent: Wed, May 3, 2017 2:45 pm
Subject: Re: [Milsurplus] Mystery Signal Corps (?) module



2600 Hz was the standard supervisory tone frequency and I've also heard of 2400 in cases where each side required separate control and there were cases when there wasn't audio path isolation. Using the tone eliminates the need for a copper connection for circuit busy/idle control. There might be tone oscillators and/or detectors associated with the relays. 


No idea what this particular device was specifically for though. 




Peter


On May 3, 2017, at 12:33 PM, Nick England <navy.radio at gmail.com> wrote:




Any ID on this?
http://www.antiqueradios.com/forums/viewtopic.php?f=5&t=320645


The binding posts look like some wireline device.




Nick England K4NYW

www.navy-radio.com





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