A radio system comprises a radio (1) having a transmit mode activated by a press to talk (PTT) switch (16) mounted on a universal communication interface (12) for mounting on a radio interface (6) associated with the radio (1). The radio interface (6) may or may not form part of the radio (1) and a plurality of radio interfaces may be provided for different applications, such that a standard universal communication interface (12) can be used with different types of equipment.