Abstract: A status indicator for monitoring a fuse or a circuit breaker, including optically isolated triggering and alarm circuits which can be integrated into a fuse holder or circuit breaker housing. More particularly, a status indicator having an LED connected in series with a fuse or circuit breaker across a power source, and a phototransistor arrangement, connected across the power source, in series with an alarm circuit. The arrangement is configured so that as long as current flows through the fuse or circuit breaker, the LED produces light which causes the phototransistor to be maintained in a non-conducting state, and the status indicator to remain in a non-alarm state. Upon failure of the fuse or circuit breaker, current flow to the LED is interrupted, resulting in the phototransistor being biased into a conductive state, and the alarm circuit being activated.

Abstract: A pulse generator circuit provides output pulses that vary in frequency in accordance with a digital input word. An external source frequency produces a predetermined number of pulses over a fixed time interval with the pulse generator circuit selecting the desired number of pulses from those in this interval to provide at its output. Any number of the pulses between zero and the total number in the interval may be selected. To assure their distribution over the interval, the pulses are arranged to occur in sets with the pulses of a given set occurring in the middle of the pulses of another set in order to prevent the bunching of selected pulses into any part of the interval. The sum of the pulses in the combined sets then provides in accordance with the digital input word the desired frequency which ranges up to and includes the source frequency.