Patent ID: 7545833

Claim:
A receiver for a door activation system, the receiver having frame timing, the receiver comprising: means for receiving an incoming RF signal; means for determining frame timing of the incoming signal; and means for adjusting the frame timing of the receiver to be closer to the frame timing of the incoming signal, wherein the incoming signal comprises at least a first and a second frame and wherein the means for determining frame timing of the incoming further comprises: means for determining the time difference between the receipt of the first frame and the second frame of the incoming signal; means for determining frame timing of the incoming signal based on the time difference; means for determining if the time difference is valid for use in determining frame timing; and means for rejecting non-valid time differences, such that receiver frame timing is not adjusted based on invalid time differences, and wherein the first frame and the second frame comprise a first frame start bit and a second frame start bit respectively, the first and second frame start bits each having a falling edge, and wherein the means for determining time difference between the receipt of the first frame and the second frame comprises: means for detecting the falling edges of the first and second frame start bits, such that the time difference is determined by the time difference between detection of the falling edge of the first frame and detection of the falling edge of the second frame.