This invention includes a switching circuit that allows a cellular phone with an audio accessory to arbitrate between cellular telephone calls and other audio inputs. In one embodiment, a cellular telephone having a MP3 accessory uses the invention to automatically switch a single set of speakers from the stereo MP3 signal to the mono phone signal whenever a call is transmitted or received. An advantage of the invention is that the user need not switch between music and phone call when the phone rings, as the invention takes care of this automatically.