A portable communication system (100) maintains mission critical functionality. An accessory (120) and a handset (130) are tethered and interoperate such that the accessory operates as the primary controlling device and the handset operates as a secondary device. The accessory (120) contains a main applications processor (102) that handles non-mission critical functions. The accessory further contains a mission critical processor (104) for handling mission critical functions of transmit and receive audio as well as PTT and emergency. In response to a failure of the mission critical processor (104), the mission critical functions are maintained by handing over the mission critical functions to the non-controlling device in a manner transparent to the user. The handover is triggered in response to status changes of the mission critical processor or as a result of battery depletion. Audio paths are re-routed through backup paths (146b, 148) negating reliance on processors of the accessory (120).