Counters and hour meters measure process run time of manufacturing or automation equipment or count a variety of occurrences, from event attendance to electrical signals. Counters, hour meters, and totalizers verify equipment running time or count how many times a process runs. Mechanical and hand tally counters manually increase their count by one with each manual push of a lever or button. Frequency counters sum up the number of specific signal changes. Counter and hour meter accessories augment existing functions or keep counters and hour meters in good working order.