Abstract: An interface connects a data processing unit to at least one working stat including data transmitting and receiving devices, such as peripheral devices. The interface includes a transmitter/receiver circuit for a station at the unit and a transmitter/receiver circuit associated with each of the devices. Data are transmitted between the circuit at the unit and the circuit at the device by a pair of transmission lines, whereby data are exchanged between the unit and the devices sequentially, character by character. Each of the characters is formed by the sequential transmission of bits along the lines. A dialogueing sequence between the unit and one of the devices is initiated when a first character is derived from the unit transmitter/receiver circuit.