ES348491A1 - Pulse Length Discriminator Circuit - Google Patents

Abstract

Signals from an inductive loop vehicle detector 1 are fed to a circuit including three relays A-C which produce four output signals I-IV the nature of which indicate whether the vehicle passes through the detection zone within a time t o or remains in the zone for a longer period. Relay A operates as long as the vehicle is detected and through its contacts 18 and 19 connects the signal source V, e.g. a positive potential, to the output I. Contacts 15 and 16 operate relay B which connects the source V to the output II if relay A lapses before the expiry of the time t o , relay B is held on for a short time afterwards through capacitor 26, and an output appears at III via contacts 17, 18 and 21, 22. If relay A remains operated for more than the time t o , the capacitor 47 charges sufficiently to fire the thyratron 2 thereby energizing the relay C. This provides an output at IV, and the output at II ceases after a short delay owing to the opening of contacts 31 and 32. When relay A lapses, contacts 11, 12 short-circuit the timing circuit. The signal IV continues for as long as signal I plus a short delay caused by capacitor 50 which holds relay C on for a short time after the opening of contacts 15 and 16.