A method of transmitting wireless messages in a communications system (201) having a plurality of transceiver units (203) for receiving and onwardly transmitting wireless messages is disclosed. In a first mode of the system, messages are transmitted from a first transmitter to a target receiver by sequential transmission via at least one transceiver unit (203). In a second mode, a wireless message containing information identifying a target receiver is transmitted from a first transmitter. The target receiver transmits an acknowledgement signal in response to receipt of the message, and at least one of the transceiver unit (203) transmits the message if that unit does not detect within a predetermined period the acknowledgement signal or transmission of the message by a predetermined other transceiver unit (203).