Ok 2fingers & Gary:

Parts you'll need from Volvo are:

1. The headrest with the microphone & speaker.
2. The headrest cover (if you have leather upholstery). If you have fabric, you can re-use the cover since the sound will pass through it.


Parts you'll need from your local electronics supply are:

1. A three lead micro-mini (2.5cm) STEREO plug w/wire attached. Trust me, soldering in the three leads is not worth the $1.00 you save by buying the plug & wire separately.
2. A zener diode equal to or greater than the voltage of the phone's output. (3-5 volts). I used a 6 volt diode.
3. Shrink-tube insulation.
4. Rosin-core solder and a 40watt iron.
5. Stranded copper wire 20 or 22 guage.


Parts you'll need from the local pawn shop: An amplifier with LINE-Volume input (RCA jacks). I got 120 watts bridged. That is more than enough.


Parts you'll need from your doctor: Tranquilizers.


PROCEDURE:

Remove the old headrest.

Install the cover (see above).

Then feed the gray wire attached to the new headrest assembly down through the hole for the headrest post along the side of the seat and out the bottom. I used 1/8" rigid plastic tubing from the top and after it cleared the bottom of the seat side panel near the seatback hinge, I taped twine to it. Then I pulled the twine back through the top hole, taped it to the gray wire and pulled same back through. Secure the headrest.

NEXT...

1. I just cut off the DIN connector from the headrest to expose the 5 wires: There is one (1) red, one (1) white, two(2) black and (1) braided ground.
2. The red wire is + for the speaker and the white wire is + for the mic. The two black wires are - for both.
3. Attach the red wire from the PLUG to the center pin of an RCA connector. Put the insulation on before you connect so that you can slide it over the joint and shrink with a lighter. Follow this insulation procedure for all connections.
4. Attach the microphone white wire to the white wire of the PLUG.
5. Now, here is the tricky part. By trial and error figure out which black headset wire comes from the microphone. Solder the anode end of the zener diode to the black wire from the headset microphone (so that the current flows from the microphone toward the PLUG only).
6. Attach the black wire from the PLUG to the RCA connector's ground terminal.
7. Solder the cathode (banded) end of the zener diode also to the black wire that goes to the PLUG. Insulate everything well.
8. Secure everything with plastic wire ties and enclose within a section of wire loom. I attached this "module" to the bottom of the seat's rear cross rail.
9. Connect a fused power wire for the amp to the battery and run it through the firewall grommet.
10. Run the wires for the amplifier's power, RCA connector, speaker wires from the amplifier under the interior trim strips next to the doors and on to the trunk or back of wagon.
11. Secure amp in trunk and connect ground wire from amp to car body. Connect the power feed to the amp.
12. Connect RCA connector to L or R LINE-IN on amp.
13. Connect the same (L or R) + out from the amp to the red wire going TO the speaker.
14. Connect the same (L or R) - out from the amp to the black wire going TO the speaker.

Insert mini-micro plug into phone jack. You should now hear through the speaker and be able to talk into the microphone on full duplex.

Adjust the potentiometer on the amp and/or bridge the channels as necessary to achieve a volume level adequate for use at all speeds. If you desire, you can add an in-line volume control. I just use the phone's volume control to fine tune the speaker.


NOTE : You will be adding/splicing wire at several points to route everything to where it needs to be and also depending on where you locate the phone. You can use colored tape to indicate the wire's color.

This is the edited version from earlier today. Post if you need additional assistance.

Bryan