[Collins] 312B-4

[Jim Brannigan]

The 312B-4(5) consoles are nice additions to the shack, but the Phone Patch
circuit is largely unused.

I remember using the Phone Patch and it worked much better than anything
else on the market.  It would seem be tailor made to use as a PC sound card
to radio interface.  (RTTY, PSK, WSJT, ATV,Voice contesting)  I used the
S-line on RTTY with a PK-232 and it worked great, but needed another set of
patch cables.

One method would be to disconnect the Phone Patch circuitry, build an
interface into the cabinet and  use the switch to handle the audio lines.
It would be easily reversible, but a waste of fine components.

Another, use a relay, controlled by RS-232 "PTT" to switch between the sound
card audio IN and OUT.  The sound card might not be happy with the 600ohm
balanced input of the Phone Patch, so additional transformers could be used.

Yet another would be to slightly modify the existing circuit and use each
side of the phone line input as un-balanced.  vs. ground.

Has anyone tried this or thought about it?

Jim