Rolling code security system
AssigneeThe Chamberlain Group, Inc.
InventorsBradford L. Farris, James J. Fitzgibbon
Life of this patent
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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. 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.
Claims9
A receiver for receiving an encrypted signal from a transmitter and for generating an actuation signal, comprising:
- receiving apparatus for receiving an encrypted radio frequency signal;
- a demodulator for demodulating the encrypted radio frequency signal into a demodulated encrypted signal;
- code separating apparatus for synchronizing with and separating the demodulated encrypted signal into a variable code portion and a fixed code portion;
- testing apparatus for testing the fixed code portion and generating a portion receipt signal in response thereto;
- window testing apparatus for testing whether a rolling code value is within a windowed range of rolling code values to avoid false triggering on a spurious rolling code having been transmitted by a person not having permission to authorize generation of the actuator signal and producing a rolling code signal in response thereto;
- a code updater for updating the variable code to an incremented rolling code;
- and
- signal generating apparatus for producing an actuator signal to produce an actuator command in response to the verified fixed code portion and the variable code.
A receiver for receiving an encrypted signal from a transmitter and for generating an actuation signal, comprising:
- a receiver for receiving an encrypted radio frequency signal;
- a demodulator for demodulating the encrypted radio frequency signal into a demodulated encrypted signal;
- a first comparator for comparing the encrypted signal to a first plurality of signal code values defining a valid signal window and in response thereto generating an actuator signal;
- a second comparator for comparing the encrypted signal to a second set of values and generating a security code signal in response thereto;
- a third comparator for comparing a second signal transmission;
- and
- a fourth comparator responsive to said security code signal for comparing a second successive transmission to said second window values and producing an actuation signal in response thereto and an inhibitor for inhibiting actuation responsive to receipt of a signal having a value within a trailing signal window.
A receiver for receiving an encrypted radio frequency signal from a transmitter and for generating an actuation signal, comprising:
- a receiver for receiving an encrypted radio frequency signal;
- a demodulator for demodulating the encrypted radio frequency signal into a demodulated encrypted signal;
- a rolling code generator responsive to the demodulated encrypted signal for producing a rolling code signal;
- a forward tester for testing whether the rolling code signal is within a forward rolling code window and generating an actuation authorization in response thereto;
- a backward tester for testing whether the rolling code is within a backward rolling code window and inhibiting actuation of an actuator in response thereto;
- a resynchronization tester for testing whether the rolling code is within a rolling code resynchronization window and generating a resynchronization signal in response thereto;
- a rolling code resynchronizer for resynchronization of a receiver rolling code value in response to the resynchronization signal;
- and
- a control signal generator for generating a control signal in response to the actuation authorization for control or actuation of the actuator.
Dependencies are inferred from the claim text.