My CLK 230 has the telephone buttons on the steering wheel, but it doesn't have a telephone, so wondered what I need and where can I get the parts required?
As Ted has said, you need the rest of the telephone pre-install package fitted in the top part of the arm rest. The top opens sideways if you have it, like this
If you have this wiring pre-installed you then need a phone cradle or bluetooth adapter to plug into it. Bluetooth adapter below
Most Mercedes have the telephone buttons on the steering wheel and audio system, but not all have the wiring. Without the wiring pre-install they are useless. Retro fitting of the Mercedes system is very expensive and a lot of owners go for after market fitments. Do a search on here for telephone cradles.