Abstract: Ultrasonic remote control receiver wherein reference frequency pulses are counted during a counting cycle comprising a predetermined number of received command signals, each command signal occupying a different frequency channel. At the end of each counting cycle, the reference frequency count is compared with the count during the preceding counting cycle. A validated output from the receiver occurs only after a predetermined number of uninterrupted identical comparisons have occurred. Interference with a validated output signal by spurious received signals e.g. noise signals is minimized by providing for invalidation of an output signal only after a predetermined number of uninterrupted non-identical count comparisons. Two of the receiver outputs are used to generate a variable duty cycle pulse train, one output increasing and the other decreasing the duty cycle. A receiver is disclosed in the context of a TV broadcast receiver wherein the variable level d.c.