A telephone handset (1), e.g. a mobile phone, is equipped with an add-on module (41). Thereby, the module (41) comprises a microphone unit (9a) which is operated instead of the microphone unit intrinsically provided in the handset (1). Further, the module (41) comprises a shortrange wireless transmission unit (23a) which is operated instead of a speaker unit (7) which is intrinsically provided in the handset (1). The short-range wireless communication unit (23a) establishes communication with a respective short-range wireless communication unit (19a) in a hearing device (10) as soon as a distance between the telephone handset (1) and the hearing device (10) drops below a predetermined threshold value as detected by a distance detection unit (21').
