Rolling code security system
AssigneeThe Chamberlain Group, Inc.
InventorJames J. Fitzgibbon
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Abstract
A rolling code transmitter is useful in a security system for providing secure encrypted RF transmission comprising an interleaved trinary bit fixed code and rolling code. To provide even greater security, the transmitter is limited in the number of times it may perform a resynchronization procedure. A receiver demodulates the encrypted RF transmission and recovers the fixed code and rolling code. Upon comparison of the fixed and rolling codes with stored codes and determining that the signal has emanated from an authorized transmitter, a signal is generated to actuate an electric motor to open or close a movable barrier.
Claims21
In a barrier movement system comprising a receiver for storing an expected code which responds to rolling codes transmitted by a transmitter, the method comprising:
- resynchronizing the receiver to the transmitted rolling code when a first predetermined condition exists between a transmitted code and the stored expected code;
- establishing a second predetermined condition;
- detecting whether the second predetermined condition has been met;
- and
- inhibiting the performance of the resynchronizing step when the second condition has been met.
The method of claim, 1 wherein the first predetermined condition represents a number of code transmissions from the transmitter.
Dependencies are inferred from the claim text.