Abstract: A system for the detection and recognition of a particular sound pattern including an initial frequency discrimination circuit comprising either band pass filters of pre-selected frequency or IC phase-locked loop tone decoders. A sequence detection circuit is responsive to the frequency discrimination circuit to successively enable paired timers upon detection of audio tones in the proper sequence and frequency. Out-of-sequence tones disable the circuit. A trigger pulse is then sent to a counter chain and successive pulse must be received by the counter chain in a predetermined time period to actuate a traffic signal control relay. The system used for a traffic signal control further includes a direction differentiation circuit to cause red lights in one direction and green lights in another as determined by the direction of the source of the sound pattern.