94 S-class

Had my radio out and noticed 3 plugs connected to nothing sitting in the dash behind the radio. Two plugs were female inline with 4 round holes of which one appears to be a ground,wire is covered and black. The other plug is a single female plug on a black wire coming from a green wire. There is also 3 bayonet type ends coming out the middle of the back of the radio with nothing connected to them. The Radio is a Becker 1492.
Anyone familiar with this stuff and can you please explain what these plugs are for?
TIA

Bump