[Collins] Re: Digital Modes with the S-Line?

[JAMES T BRANNIGAN]

 I see requests for sound card to radio interfaces for digital work.

 Don't overlook a creative use of the phone patch circuit in the 312B-4/5
 consoles.
 If you are fully "wired up" then the console is connected to RX/TX audio
and
 PTT.
 It also contains matching transformers and some RFI protection.
Mic/speaker
 switching is built in.

 The "problem" is connecting the two sound card IN/OUT plugs to the single
 600 ohm connection on the phone patch.
 There are several ways to do this.
 1) just hook it up and see what happens.
 2) use a resistive network to isolate the sound card ports.
 3) use a relay to switch them (run it off the PTT)
 You might have to play with the sound levels.
 600 ohms should be OK for the sound IN, but you might need a 600 to 3.5 ohm
 transformer for the sound OUT.  (Radio Shack has them)

 I tried this "receive only" and it worked fine.  I have not tried it for
 transmit.

 Jim