Mobile device accessory with interworking circuit switched and internet protocol based voice channels

摘要

An accessory device (31) to a mobile device (34) is described that enables a mobile device to have voice over internet protocol based voice calling functionality that can optionally fall back to circuit switched voice functionality. This is achieved by providing an accessory device (31) that couples a voice over internet protocol voice channel (32) with a circuit switched voice channel (33) such that a user is able to switch from one channel to another with or without user intervention.