Wiz
Thanks for the info. Much appreciated.
I'll talk to Autocom but looks like I'll be wiring as you described (seems same setup as Brian on Razorbike who used 2 x #1314 leads from Autocom which are isolated to reduce interference)
The use of phone is not a priority for me but fully functional music, in stereo, Bike-to-Bike and the satnav prompts is.
By the way Wiz, "isolated leads from Autocom" is this the same as "ground loop isolater" you mentioned. Drawing would be great. Autocom leads are expensive.
No probs. Yes, the "ground loop isolator" (GLI) is a generic name for the thing Autocom sells for about £25

. Cheapest place I've found to get one is
here:, you can also get them from Maplin
here: . If you already have the Autocom one, you can use that as well no probs.
The wiring is simple really. I know why Autocom got it wrong and I'll try to explain below, but let me make the wiring clear first.
Music: stereo socket on the Zumo into the GLI then from the GLI into the music in socket on the Autocom.
Phone: OK, the phone socket on the Autocom has 3 poles: Speaker, Mic and Ground:
round tip = microphone
ring = speaker
sleeve = ground
The Zumo "Mic" socket only has a two polls on it (mono). It doesn't need the third poll because it only carries the mic signal, not the audio one. The Music-out socket from the Zumo carries both the Stereo music signal AND the mono audio signal from the phone. So, on the mic side, you'll have two wires coming from the mono mic jack socket on the Zumo, which need to be soldered to the mic and ground polls of a 3 poll (Stereo) jack that will go in to the Autocom. The mic lead does not need to go through a GLI because you are not carrying any audio in that cable. The middle ring of the jack plug is not used, that would usually carry the mono phone speaker signal.
OK, what both Autocom and Starcom have done is to connect the left and right speaker signal wires from the stereo socket together making one combined signal and have put that into the mono phone-in socket on the Autocom (or Starcom). This is frankly a crap arrangement, because not only do you get mono sound, but the phone circuitry in the Autocom is not designed to carry a quality music signal - only basic speech. It also means (as discussed above) that the music will not mute to 50% when you receive speach via your PMR radio.
I can only think that Autocom wired their lead this way because they mistakenly thought that the Autocom would get confused and keep halving the volume if you feed speech into the music socket, but it won't, because thee is no audio going into the phone socket that will trigger the 50% mute function. The music will cut out completely when you get a call because the Zumo will automatically pause it.
Ok if you have got this far without nodding off and still have any questions feel free to PM me or email me at wiz (at) bikersoracle.com
I do know a couple of the tech guys at Autocom so I'll speak to them about it over the next couple of days and see if they'll amend their lead.