Abstract: A car security alarm system includes a receiver portion incorporated in a car electricity system and in electrical/mechanical connection with associated parts/systems of the car and a transmitter portion to be carried by a driver of the car. The transmitter portion repeatedly emits a predetermined signal including an identification code at predetermined intervals. The receiver portion includes a receiving circuit to receive the signal and an identifying circuit to determine if the identification code is correct and apply a confirmation signal to a central processing unit in case the identification code is correct and the central processing unit generates an instruction to unlock the car door in the situation that the car security alarm system is in activated condition. In the condition that the system is in de-activated condition, if no such identification signal is detected by the receiver portion within a predetermined period, then the central processing unit generates a signal to lock the car door.