A method of operating a telephone device, having a plurality of telephone jacks, connectable with an audio unit, a plurality of speakers, and a plurality of microphones, all located in a vehicle. The telephone device connects to the audio unit through the telephone jacks where parameters are set for the telephone device to perform a telephone operation. The telephone device receives an incoming telephone signal through one of the telephone jacks, and transmits an outgoing telephone signal through one of the telephone jacks that is selectively activated to perform the telephone operation.