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Security system and method therefor

  • US 5,781,121 A
  • Filed: 03/22/1996
  • Issued: 07/14/1998
  • Est. Priority Date: 03/24/1995
  • Status: Expired due to Term
First Claim
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1. A security system for an automotive vehicle, which comprises a transmitter (1) and a receiver (11) that cooperate to produce a control signal for actuating a security device, and wherein the transmitter (1) comprises:

  • a number generator (4) for sequentially generating numbers ai, ai+1,a transmitter-end calculation unit (6) for sequentially calculating transmitter variables di, di+1, based on a predetermined operational expression using the respective numbers ai, ai+1, as a constant, anda transmitting unit (8,9) for sequentially transmitting data to the receiver (11), wherein the data comprises a transmitter variable code obtained by encoding the transmitter variable di and a constant code obtained by encoding the next generated number ai+1, andwherein the receiver (11) comprises;

    a receiving unit (14,

         13) for receiving the data from the transmitter (1),a receiver-end calculation unit (15) for sequentially calculating receiver variables ei, ei+1, based on the predetermined operational expression, using, respectively the sequentially received numbers ai, ai+1, represented by the constant code in the data received from the transmitter (1), anda controller means (15) for comparing the calculated receiver variable ei with the transmitter variable di represented by the transmitter variable code in the received data, and for outputting a control signal, in response to an affirmative comparison, for actuating the security device.

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