The present invention is an anti-theft system for the surveillance of computers and high-risk electrical and electronic equipment. This system is based on activating an internal transmitter contained in the stolen equipment. In the case of stationary equipment the activation of the transmitter is carried out by the external power supply being disconnected. In the case of mobile equipment, the transmitter/transceiver is activated by an external power supply disconnection, in addition to a software command with password or remote control. The transmitter then emits encoded signals that are received by a receiver and causes the activation of an alarm system located at the checkpoint.