this really belongs in audio...so I'll move it there.
If you search for radio pinout on the forums you should find the diagram you need posted many times over.
And the radio is not tied to the alarm in any way.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>