The present invention regards a communication system (10; 10a; 10b; 10c) comprising at least one communication device (36, 36a, 36b, 36c) configured to connect to other communication devices (36, 36a, 36b, 36c) via an audio and data link (52). The communication device (36, 36a, 36b, 36c) comprises at least a receiver unit (40), an output transducer (32), a microphone (22, 22′), a transmitter unit (42), and a control unit (38). The receiver unit (40) is adapted to receive audio signals and data signals via the audio and data link (52). The output transducer (32) is adapted to stimulate the hearing of the user (12, 20, 30) according to the audio signals received via the audio and data link (52). The microphone (22, 22′) is adapted to receive input sound (44) and generate an audio signal from the received input sound (44). The transmitter unit (42) is adapted to transmit audio signals and data signals via the audio and data link (52). The control unit (38) is connected to the receiver unit (40), to the output transducer (32), to the microphone (22, 22′), and to the transmitter unit (42). The control unit (38) is adapted to control the signal transmission between the receiver unit (40), the output transducer (32), the microphone (22, 22′), and the transmitter unit (42). The control unit (38) is further adapted to generate a data signal corresponding to the communication device (36, 36a, 36b, 36c) for identifying the communication device (36, 36a, 36b, 36c). And the control unit (38) comprises a processor (46) which is adapted to process audio signals and data signals. The communication device (36, 36a, 36b, 36c) is connectable to an attachable digital receiver (26) via the audio and data link (52). The attachable digital receiver (26) has a shape that matches a shape of a hearing aid (28) in order to be attached to the hearing aid (28). The communication devices (36, 36a, 36b, 36c) of the communication system (10; 10a; 10b; 10c) can be Smartphones.