Abstract: An anti-theft system for cars and the like. A receiver is mounted in the trunk of the vehicle. A first receiver wire is connected to the electrical system of the car for supplying power to the receiver only when the ignition switch is turned on. A second, normally grounded, receiver wire is extended to the ignition coil for preventing operating of the ignition system. To remove the ground from this second conductor, it is necessary to operate a small transmitter while the ignition switch is turned on. The transmitter and the receiver are sold as a pair, the receiver being tuned to recognize a coded signal from only the paired transmitter. Once the ignition system is turned on, the disabling ground potential is held removed from the second conductor even though the transmitter is no longer operated.