Batboard

I've been doing some work on a SmartNet II single-site system lately. It's 10 channels, non-simulcast, non-voting. It's console is Centracom Gold Elite.

There are TBIM's and TIMI links that come from the dispatch center to the central controller (a 6809 SmartNet II+ Central Site Controller). The stations are MSF 5000's.

What I'm curious about, is when a unit calls dispatch and dispatch responds, you can hear a short burst of what sounds like 2175Hz which is then ALMOST completely muted, and when dispatch unkeys, you can hear a little "cheep" of 2175Hz....

Almost sounds like the 2600Hz idle tone you'd hear on Ma Bell's old telephone exchanges.

Why am I hearing this 2175Hz tone? What generates it?

I kinda like it - would be nice if it could be implemented on my conventional ham system... I have a T5600 connected to an MSF 5000 via a DigiTAC.

Thanks for any help.

From memory the TBIMS generate a tone on keyup
Also if your centracom is a remote CEB there is a tone on the audio lines between the CORI and the ROCI

The CEB is in the same building as the consoles, but there are TIMI links with modems between the CEB and the CSC.

Still wondering where the tone comes from.