Portable telecommunication apparatus for multiple audio accessories

A portable teleconmnunication apparatus, comprising:

• an audio input for receiving sound;
• an audio output for generating sound;
• a controller for controlling the audio input and the audio output;
• and
• an audio accessory interface for operatively connecting at least two audio accessories, each audio accessory being capable of receiving external sound and forwarding it as an audio signal over an audio interface to the apparatus and being capable of generating external sound in response to audio signals supplied from the apparatus over the audio interface,
• wherein the controller is arranged to receive over a control interface a request for an audio service from any of at least two audio accessories operatively connected to the apparatus, the request for audio service from any of the audio accessories including a first command specifying a number of audio parameters for a particular audio mode and at least one secondary command specifying one of a plurality of audio functions to be performed by the portable telecommunication apparatus in accordance with the specified audio parameters, and
• wherein the controller includes a logical state machine, the individual states of which represent possible operational conditions for the portable telecommunication apparatus and the at least two audio accessories, the state machine defining how the request for audio service, including the first and second commands, is to be serviced by the portable telecommunications apparatus, the controller being arranged to provide the audio service to any of the audio accessories as defined by the state machine.