Being the area along the railroad line

摘要

PROBLEM TO BE SOLVED: To detect a fault on an on-railroad telephone set system at an early stage. SOLUTION: An automatic monitoring function is provided in the on-railroad telephone set system. Intra-telephone monitoring devices conducting the monitoring test of a telephone set circuit are provided in on-railroad telephone sets with the opening/closing of the door of a casing as a condition. A center monitoring device is provided on the exchange network side of a telephone line group and a line remote end monitoring device at the far end of the telephone line group. The center monitoring device collects the monitoring result of the intra-telephone set monitoring devices and opening information of the door through a monitoring-only communication line. The center monitoring device and the line remote end monitoring device have test circuits transferring a test signal with opposite devices through the telephone lines and detecting the fault of the telephone line. The center monitoring device and the line remote end monitoring device transfer control information required for the test through the monitoring-only communication line.