Wayne wrote:

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?

Pins labled 1-8 (Right to Left across top of connector)
J-A ( " " " " bottom " " )

7 A/C Mic Key Line
B A/C Phone Bus
D Dimmer
C Dimmer
1 14/28V Power
J Phone Audio Out (my guess: wire all headset jacks in parallel)
6 Pilot Mic Key (my guess: wired to switch in Pilots yoke)
8 CoPilot Mic Key (my guess: wired to switch in CoPilots yoke)
A A/C Ground
F A/C Mic Audio
E Pilot Mic Jack
H CoPilot Mic Jack
2 Pass1 Mic Jack
3 Pass2 Mic Jack
4 Pass3 Mic Jack
5 Pass4 Mic Jack

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.

Two diodes inside the Isocom could do this?

I assume that the mic's
for the rear are completely isolated from the com radios but am not really
sure.

Appears that each mic has its own bias source, but likely the audio from
all mics is summed ahead of the intercom squelch circuit.

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?

My guess is that it can support up to 6 stations...
No splitter required; just wire all four (up to six) headset jacks in
parallel

I really wish I had my hands on an installation
manual.

I dont have one.

MikeM
Skylane '1MM
Pacer '00z