Importance

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Abstract

A transmitting unit of a wireless security system having randomized successive ('rolling') verification codes transmits a different synchronization code each time that the transmitter unit is powered up. After power up, a pseudo-random value is generated by a pseudo-random number generator. The pseudo-random value is at least in part dependent upon a manipulation of a manually-operable switch of the transmitting unit. The pseudo-random value is incorporated into the first synchronization code transmitted after the first power up. If power to the transmitting unit is then interrupted and then resupplied, for example by removing and then replacing a battery, then the pseudo-random number generator generates another pseudo-random value, the value again depending at least in part upon a manipulation of the manually-operable switch. The pseudo-random value is then incorporated into the first synchronization code transmitted after the second power up. The first verification code used to gain access to the automobile is generated based on an initially fixed start value specific to the transmitting unit as well as on the initially randomized pseudo-random value.

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First Claim