Abstract: A tyre pressure monitoring system comprises an initiator which is arranged to transmit an initiation signal, and at least one corresponding transducer associated with a tyre of the vehicle which responds to exposure of the initiation signal from the initiator and is adapted to respond by transmitting a return signal indicating that it has been woken by the initiator, in which the strength of the initiation signal emitted by the initiator is varied across a number of values within a range.

Abstract: A tyre pressure monitoring or warning system comprising at least one receiver (112) responsive to signals transmitted by transmitters (106, 107, 108, 109) associated with one or more tyres (102, a, b, c, d, 104) the system including a memory which stores a list (150, 152) of identity tags (156) captured by the receiver (112), and a list of associated confidence values (158) for each identity tag (156) indicative of the confidence that the stored identity tag (156) corresponds to a transmitter (106, 107, 108, 109) that belongs to the vehicle. The list may be split into a member (150) and a candidate (152) list comprising those identity tags (156) that are deemed to refer and that possibly refer respectively to transmitters (106, 107, 108, 109) associated with the vehicle respectively. Initiators (114) may be provided to initiate transmission from the transmitters (106, 107, 108, 109) in order to locate the position of each tyre (102a, b, c, d, 104).