CIRCUITRY FOR DETECTING FAULTS IN DUPLICATE CONTROLLERS

摘要

Circuitry is disclosed for detecting faults in duplicate controllers in a private branch exchange (PBX) system. The circuitry comprises a bidirectional counter which is initialized to a midpoint state and subsequently counts incrementally or decrementally trouble signals signifying noncompleted operations of the active (on-line) controller. The controllers are alternately made active at nominal 10-second intervals. Upper and lower count states of the counter define points at which a controller, identified by the upper or lower state, is generating an intolerable number of trouble signals in relation to its mate. Additional structure includes a second counter which accumulates the number of completed system operations for reinitializing periodically the bidirectional counter to the midpoint state, circuitry for detecting the upper and lower count states, storing the identity of the offending unit, and maintaining it in an off-line state.