| 摘要 |
<p>PURPOSE:To enable a call from a maintenance station during an electric power failure at an unattended exchange by calling an unattended station on the no- power-source system and by supplying a calling circuit from the maintenance station. CONSTITUTION:When unattended station SO is in a power failure, calling-signal receiving bell BEL is connected to stand-by talking circuit Ts and communication calling handset TR is connected to stand-by talking circuit Ts to hold calling-current supply from maintenance station TC in readiness. Then when connection key ON and calling key R1 is maintenance station TC are operated, a calling signal of 16Hz is sent to unattended station SO to put BEL into operation, letting a patrolling inspector know incoming. Next, the patrolling inspector operates answer key ANS to supply a calling current from maintenance station TC to handset TR, permitting a communication call. Thus, the communication call can be made even in a power failure at the unattended station.</p> |
