Initialization of a wireless security system

A security system, comprising a central apparatus and at least one detector apparatus;

• the detector apparatus comprising transmission means for wirelessly transmitting a message comprising a source identification uniquely identifying the transmitting apparatus, and detection means for detecting an alarm condition and in response causing the transmission means to transmit a message;
• the central apparatus comprising:
• memory means for storing a source identification of at least one detector apparatus;
• alarm means for raising an alarm;
• user interface means for bringing the central apparatus in a selected one of a plurality of modes, including an operational mode and a learning mode;
• and
• reception means for receiving a wirelessly transmitted message, for storing, in the learning mode, the source identification of a received message in the memory means, and for causing, in the operational mode, the alarm means to raise an alarm if the source identification of a received message is stored in the memory means, characterised
• in that the detection means is adapted to cause the transmission means to transmit an alarm message in response to detecting an alarm condition;
• in that the detector apparatus comprises means for causing the transmission means to transmit a learn-detector message in response to a learn trigger;
• said learn-detector message being distinct from said alarm message;
• in that the reception means is adapted to cause the alarm to be raised in response to receiving an alarm message, and to store the source identification only of a received learn-detector message.