Davis Clark ISOCOM pinouts

Working on a 172 with an ISOCOM panel mount intercom. There are no jacks
on the rear seats. Anyone have the pinouts for the unit? I've never got to
see the instructions for an intercom and wondered how they are wired so the
PTT only works for the guy that pushes the button. I assume that the mic's
for the rear are completely isolated from the com radios but am not really
sure.

I have seen people use splitters for the headsets, anyone know if the
change in impedance would hurt the little amp chips or are all headsets
paralleled into one channel? I really wish I had my hands on an installation
manual.

Thanks

Wayne
PP-ASEL
63.9 Hours