Sony Ericsson Car Handsfree Mute wire

[Spanky]

I don't have an oscilliscope and I haven't put the DMM on it yet but can
anyone tell me what output the 'music mute' wire supplies in a Sony Ericcson
car handsfree system? Does it go low, high or does it pulse?

 

[Spanky]

So when there is no call the mute wire should be floating and when a call
comes in the mute wire should go to earth?

 

[Brian Goldsmith]

The mute wire puts out a constant earth.
Depending on the model of phone and car kit it is usually the following
red - +12V ACC
yellow- +12V Constant
Black- Earth
Green- Mute


*** If it puts out a constant earth,then how does it do anything except
connect something else constantly to earth???????????????????????????

Brian Goldsmith.

 

[Spanky]

Thanks.

The mute wire is switched to earth when the car kit is used.This is done by
a minature relay inside the databox.Once the phonecall is terminated the
relay is released therefore removing the earth from the mute wire.

Cheers
Joe