Remote control security system for automobile issuing a fixed basic code and two variable codes

In a remote control security system for an automobile, comprising a remote control unit, connected to said receiving unit;

• said remote control unit emitting a combination code signal and said receiving unit receiving said combination code signal so as to control operation of said security system:
• wherein said remote control unit includes a keyboard, an encoder and a signal emitter;
• said encoder produces a combination code corresponding to said combination code signal according to a signal from said keyboard, and said combination code is transmitted by said signal emitter;
• wherein said receiving unit includes a receiver and a decoder;
• said receiver receiving the combination code signal sent by said emitting means of said remote control unit and said decoder including means for comparing said a received combination code decoded from said combination code signal with a combination code produced by said decoder;
• and
• wherein if the received combination code matches the combination code produced by the decoder, a control signal is transmitted to said operation unit to control operation of the security system,
• the improvement wherein the combination code comprises a fixed combination code and two variable remedy codes, and said encoder and decoder each includes means for sequentially varying a first of the remedy codes once each time a key on said keyboard is pressed, and for sequentially varying a second of the remedy codes constantly between a time that said key is pressed and a time that said key is released.