RF protocol with variable period wake-up

A remote wake-up assembly is provided including a remote device containing logic adapted to: generate a pre-amble signal comprising a plurality of pre-determined signal pulses sequentially varied throughout a pre-amble period; and generate a main message signal after a wake-up time-period. A receiver system is included containing logic adapted to: poll for the signal pulses, the receiver system polling comprising an on-state having a on-state length sufficient for receiving at least two of the sequentially varied signal pulses; determine the wake-up time-period using said at least two of the signal pulses; place the receiver system into a low-power sleep state during the remaining portion of said wake-up time-period; reactivate the receiver system at the end of the wake-up time-period; and receive the main message.