Abstract: A keyless security system which has eliminated the need for providing a vehicle-mounted receiver with an electric field detector, thereby achieving a simpler construction with resultant lower cost. The keyless security system is equipped with a portable transmitter for transmitting a remote control signal for locking and unlocking a vehicular door lock mechanism and a vehicle-mounted receiver which has a signal receiver for receiving the remote control signal, a signal processing unit for processing the remote control signal, and a control unit for monitoring each section of the vehicle and also for controlling the entire system. The control unit and the signal receiver are placed periodically in an activated condition and a standby condition. When the control unit detects the electric field of a received remote control signal, the control unit and the signal receiver are placed in a continuously activated condition.

Abstract: A security system including a remote control unit and a vehicle-mounted security apparatus. The remote control unit includes a first cyclic-code generator for generating a first cyclic code in accordance with a predetermined sequence when a key on the remote control unit is depressed. The first cyclic code is added to a command code, which is determined by the depressed key, and is transmitted as a remote control signal. The security apparatus includes a second cyclic code generator which produces a second cyclic code in accordance with the same sequence as used by the first cyclic code generator. When the security apparatus receives the remote control signal from the remote control unit, the security apparatus decodes the first cyclic code from the command code, and compares the first cyclic code with the second cyclic code. If the first and second cyclic codes coincide, the apparatus executes the operation determined by the command code.