Circuit for distinguishing specific pulse patterns in a pulse train.

摘要

A circuit for recognising cyclically occurring pulse sequences includes a counter (13) controlled by a D-type flip-flop circuit (12) to start counting the pulses in the pulse sequence when a specific pulse event occurs. The output of the counter (13) is compared by a comparator (16) with a preset number to provide an output via a gate (26) if the specific pulse event occurs when the number of pulses counted by the counter is equal to a preset number. If the count rises above the preset number the comparator (16) resets the flip-flop and no output is produced by the gate (26).