Abstract: An overcurrent protection system has an adjustable inverse-time characteristic which may be varied at will. The output of the inverse-time characteristic determining circuit is coupled to a variable timing means which is used to further shift by a predetermined time the inverse-time characteristic of the system, thereby providing a greater variety of possible switching characteristics. Further provided is an adjustable return-to-zero circuit which still further varies the characteristics of the protection system.

Abstract: A fault detection and signaling system is responsive to a fault detection to generate a first type of warning signal indicative of fault detection and includes means operable to indicate that a fault is "acknowledged" and for causing the generation of a second type of warning signal if the fault still exists and to cause ceasing of generation of the first type of warning signal if the fault no longer exists. Further provided is means responsive to fault detection by another fault detection and signaling system for causing generation of a third type of warning signal when a fault is indicated by the present system subsequent to a fault detection by another system.