Underspeed/overspeed detector

Claim 1

A detection system for determining unacceptable deviations from a desired spacing pattern in the passage of articles past a station comprising: sensing means for providing a sensed pulse signal upon the passage of an article past a station; timing means associated with said sensing means resettable to a base condition upon reception of a sensed signal and triggerable upon failure to receive a sensed signal for a pre-determined period of time thereby providing a firing signal; output means associated with said timing means actuable from a first condition to a second condition upon reception of a firing signal; and flip-flop means associated with said sensing means successively settable between a first level and a second level upon reception of successive sensed signals; said timing means also associated with said flip-flop means whereby reception of a firing signal thereby causes said flip-flop means to assume said first level; said flip-flop means also associated with said output means whereby bistable signals representative of said first and second levels and the transition signals therebetween are received thereby; said output means actuable from said second condition to said first condition upon reception thereby of and only of the transition signal arising due to the excursion of said flip-flop means between said second level and said first level.