So can i take it your car`s wheel does not have them?i will be very interested to know how you get on,as i have said there is only one wire for audio controls on the head unit that is what`s throwing me
you mean how does it interface with the stereo?
thats a little more complex,
i am personally building a translator purely for converting the signals from the wheel into useful signals, that can not only control the headunit, but maybe bluetooth adapters and also at some point after market cruise control.
but the steering wheels and headunits usually use a resistor matrix, where each button press is equal to a certain resistance. if you have an in car PC, there is an adapter that can convert resistances into keyboard presses (another useful little device that i will be using in my car) or there are some adapters on ebay that convert resistances to standard headunit signals. usually the pioneer/sony standard.
another option would be to take a remote designed for the headunit, and replace the resistors in the steering wheel with the ones in the remote. or another option (if a little crude) would be to take an infrared remote designed for the stereo, unsolder the LED and wire it somewhere where it points to the headunit, then run it to the steering wheel and wire the buttons to the steering wheel controls. it would be a bit like an optical decoder kinda thing.
but anyway there are LOADS of ways of doing it, the hardest part is finding a nice steering wheel. i spent ages getting the D40 one with an airbag, it cost more than i have paid for some cars, and it was in horrible condition and will need retriming.