A remote entry system for a vehicle includes a portable transmitter and a vehicle-mounted receiver. The receiver alternates between a monitoring state lasting for a monitoring period and a sleep state lasting for a sleep period. A remote control is manually activated and a message sequence is transmitted to the receiver in response to the manual activation for initiating a function of the remote entry system. The message sequence comprises a plurality of blocks transmitted at a predetermined block interval, the blocks including a preamble block and at least one message block. If the receiver detects the preamble block then it enters a reception state for detecting the message block. The preamble block has a predetermined preamble length and is comprised of a plurality of bytes separated by respective off intervals between successive bytes. Each off interval comprises a predetermined off period greater than the predetermined byte period. The predetermined off period is less than the monitoring period and the monitoring period is less than or equal to the predetermined off period plus substantially twice the predetermined byte period.