The present invention relates to communications systems incorporating peripheral devices such as a push-to-talk (PTT) or similar and interface cables to connect these to a headset and/or a communication device such as a man worn two-way radio, vehicle intercom system, mobile phone, etc. In particular, the invention relates to such interface cable having an integrated functionality. The basic idea of the invention is to use an interface between a first and a second device in a voice communication system, which interface is specific to the second device and holds digital information allowing the first device to identify or adapt to the second device. This allows the first device to automatically adapt its settings and/or functionality to, and thus to function with, several different second devices without any need for updating, re-configuration, or user intervention. Thus the first device can be hot swapped or hot plugged with different second devices simply by using a cable specific to each particular second device.