CARRIER CHANNEL NETWORK FAULT DETECTOR, PRIVATE BRANCH EXCHANGE SYSTEM, MULTI-ZONE TYPE CORDLESS EXCHANGE SYSTEM, AND TELEPHONE SET

摘要

PROBLEM TO BE SOLVED: To develop a device by which a user side can somehow grasp a fault or abnormality of a carrier channel network so as to automatically disconnect a faulty carrier channel. SOLUTION: An inspection section 110 inspects, when making a call, presence/ absence of reception of a reply signal from a called party or of transmission of a call tone to a caller, and discriminates it to be an incomplete call when the inspection denotes the absence of them within a prescribed time. A count section 120 increments a carrier use continuous incomplete call counter used when making the call by one each if the inspection section 110 discriminates the incomplete call and clears the carrier use continuous incomplete call counter used when making the call when detecting transmission of the call tone. A fault discrimination section 130 monitors whether the count of the continuous incomplete call counter reaches a prescribed threshold value set separately by each carrier and discriminates the occurrence of a fault in the carrier channel network when the counts reach the threshold value. A changeover section 140 stops the use of the carrier when the carrier is discriminated to be faulty and selects another carrier decided in advance.