Abstract: The anti-theft control system includes a sending module (A) for sending encoded signals on a power line (12) of a vehicle power supply (B). The sending module (A) includes a keyboard (52) on which an authorized user enters his code. If the proper code is entered, a digital encoder (40) produces a preselected encoded signal which is imposed on the power signal by an interface circuit (60). The anti-theft control system further includes a receiving module (C) which receives encoded signals from the power line. The receiving module includes a detector (70) for separating encoded signals from the power signal and a decoder (80) for comparing the received encoded signal with the preselected encoded signal. If the decoder (80) determines that the preselected encoded signal has been received, it enables an ignition control circuit (90) to pass electric power from the vehicle ignition key switch (20) to the vehicle ignition (22).

Abstract: An electronic key (A) includes an electrical plug (10) which is connected with the power, and ground, and output terminals of an encoder (20). An electrical jack (30) is adapted to receive the electronic key plug (10) to supply ground and power thereto and receive an encoded signal therefrom. A decoder (50) is connected with the jack to receive the encoded signal and produce an enable signal if the encoded signal has a preselected code. The enable signal is extended by a first latch (54) to an indefinite duration and the extended enable signal closes an enabling switch (56) and disables an alarm control (80). The enabling switch (56) allows an automotive ignition key (60) to operate the automotive ignition (62). When the enabling switch (56) and the ignition key switch (60) are closed, the first latch is reset and a second latch (68) is enabled to continue producing the enable signal of indefinite duration.