Head unit phone signal

Rortec wrote: Hi Guys, [PWhat i would like to know is what signal (+/-) is used for the mute feed?

Normally this is a (-) negative pulse, coming off from the phone. Regards EVIL Teken . . .

Rortec wrote: What voltage is this normally?

If this is a *in care phone, then it is based on a +12 volt power supply. If this phone is one which you carry in your pocket, that is dependant upon each of the phone manufacture(s). Some people have those *hands free* speaker boxs which interface with the hand held phone. At that point the phone is being powered by a +12 volt source, with a step down power supply, normally 3.80 volts aprox. Which then gets plugged into the portable phone. The mute feature is *normally* part of the hands free also, and many people interface that part of the *hands free* device to the vehicles horn. This is the same principle as the radio, that you wish to interface. Below I will list the connections for the horn honk alert, and you can apply this to your head unit, if you wish. I will provide both arrangements for positive and negative source horns that you may encounter. 85 = Output wire from phone / hands free device. (-) 86 = +12 volts fused @ 5 amps 87 = +12 volt type horn, which is grounded 30 = +12 volts tied to pin 86 ====================================================== 85 = Phone output 86 = +12 volts fused @ 5 amps 87 = Ground type horn, whitch is tied to +12 volts 30 = Ground (-) If you need to reverse the polarity for any of the units in question you will find the schematic on this site as well. If you would like me to post it, I will do so as well. I hope this gives you some insight into your project. Regards EVIL Teken . . .