Abstract: A tracking system for enabling maintenance of alignment between a receiver of electro-magnetic radiation and a source of electro-magnetic radiation signals, the system comprising: a receiver; a sensor associated, in use, with the receiver to sense the strength of the signal received by the receiver; and an interrupter device, which in use, intermittently interrupts one or more discontinuous eccentric portions of the signal being received by the receiver thereby attenuating the received signal by an extent which is dependent upon the degree of misalignment of the receiver from the transmitter.