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

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

I've got a DC ISOCOM in my bird, but have been recently looking to
upgrade. It works well, but has only one squelch setting for all mics,
opens all mics at one (not just the one who's speaking), and doesn't have
music input. I've found that these are usually pretty advanced intercom
features so I'm shopping around.

I recently got the DC ISOCOM working better, now that I managed to
google up the manual for it (very obscure link somewhere, definately not
on DaveClark.com). There are two adjustments behind the two faceplane
philips screws. If you remove them, you can put in a precision regular
about 1.5" and adjust the sidetone level through the left hole, and radio
volume through the right. The nifty thing was that the manual had an
*ACTUAL* schematic in the thing, so now I know how it works/doesn't work.
Thinking about hacking it slightly to add music input, but can't figure
out how to make it mute when the radio comes on.

-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

I got your email with the file attached. Thanks again, very much. I saw the
schematic, I knew diodes wouldn't work to isolate an AC mic source. Tgey
just call it an isolation circuit. Sorry I can't help on the auto mute.

Wayne
wrote in message
...
I've got a DC ISOCOM in my bird, but have been recently looking to
upgrade. It works well, but has only one squelch setting for all mics,
opens all mics at one (not just the one who's speaking), and doesn't have
music input. I've found that these are usually pretty advanced intercom
features so I'm shopping around.

I recently got the DC ISOCOM working better, now that I managed to
google up the manual for it (very obscure link somewhere, definately not
on DaveClark.com). There are two adjustments behind the two faceplane
philips screws. If you remove them, you can put in a precision regular
about 1.5" and adjust the sidetone level through the left hole, and radio
volume through the right. The nifty thing was that the manual had an
*ACTUAL* schematic in the thing, so now I know how it works/doesn't work.
Thinking about hacking it slightly to add music input, but can't figure
out how to make it mute when the radio comes on.

-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************