| 摘要 |
PURPOSE:To prevent a call from being disconnected due to the termination of backup by providing a power failure key telephone system with a power failure monitoring relay setting a power failure action mode where direct incoming and outgoing can be free with respect to a telephone circuit and a mode changeover switch restoring forcibly the monitor relay. CONSTITUTION:A tone ringer 38 and a speaker SP detect incoming when in a manual changeover-type main device KSU1 a switch SW0 is operated, or the relay PS is restored to connect a call line 51 directly to the telephone circuit, and a call circuit 32 executes calling corresponding to turning on a hook switch HS<2> due to off-hook. Even if the operation is backup by the battery power source B17 of the KSU1, the mode changeover switches SWS and SW of the KSU1 and the key telephone system ST61, or the SWS and the switch SW0 are operated. Then the telephone circuit is arbitrarily connected to the ST61, which simultaneously comes to the power failure action mode, and the direct incoming and outgoing can become free with respect to the telephone circuit. Accordingly the backup by the B17 is terminated, and a call with not be suddenly disconnected. |
