Help: Connecting C500 to Motorbike Intercom

[Guest Tobers]

I have an Autocom intercom on my motorbike. It has a 3-ring 2.5mm jack plug on it for connecting a mobile phone. If I plug this into the C500, the speakers in my helmet work (so I can hear TomTom etc), but the microphone doesn't work (if someone calls me, I can hear them but they cant hear me).

I realise the C500 handsfree kit has a 4-ring 2.5mm jack plug so obviously the connections dont match.

So...

1) I've bought a 3-ring 2.5mm socket into which I will plug the Autocom phone lead.

2) I've de-soldered the wires from the C500 handsfree kit at the microphone button thingy.

3) I've now 6 wires and a resistance check reveals their connections to the 4-ring plug as follows (ring 1(tip), ring 2, ring 3, ring 4 (innermost))

- white: ring 3 - speaker

- bare gold: ring 4 - common ground

- red: ring 2 - speaker

- green: ring 1 (tip) - microphone????

- bare gold: ring 4 - common ground

- dark green: ring 4 - common ground

4) I've connected these to my 3-ring socket with mike at ring 1 (tip), speakers both to ring 2, and grounds all to ring 3. This is according to the tech specs from Autocom.

Now, with everything plugged in, I can hear the phone fine through the helmet speakers (so I must have at least 1 speaker and one ground correct) but the microphone still doesn't work.

Anyone got any ideas on this? Or confirmation on the pinouts of the C500 plug.

Thanks!!

[Guest Tobers]

In case anyone is interested, more investigation reveals the following in the C500 headset:

Red wire = speaker

Green wire = speaker

White wire = microphone

Thin gold wire = headphone common/ground with volume reduction from slide thingy on the headset cord

Thick gold wire = common/ground without volume reduction

Blue = no idea

I connected red & green together onto the speaker connector of my 3-ring socket, connected white to the mike connector, and the thin gold wire to the ground connector.

I can hear sound fine through the speakers. The mike works but is very faint at the receiving end - this may be due to the mike in my helmet being a different resistance to the one in the C500 headset?

So - not entirely satisfied yet. If anyone can work out how to sort out the mike volume problem or knows what the blue wire is for, let me know.

Ta