The Video Motion Anomaly Detector addresses the problem of automatically detecting events of interest to operators of CCTV systems used in security, transport and other applications, processing CCTV images. First, basis pulses at various frequencies and pseudo-random delays are generated. The undercarriage has front and rear suspension arms supporting front and rear idler wheels. The duty cycle correction circuit may also include a second circuit to convey the output voltage during the second cycle and correct a current mismatch of the second circuit during the first cycle. The device further comprises a biasing spring, to close the valve when the rotary actuator is de-energized, and a rotary position sensor, which, in co-operation with the rotary actuator enable accurate angular positioning of the valve.