| 摘要 |
For keyphone or homephone system, it provides call capability using current for voice transmission, supplied by the telephone office, without another back-up battery when black-out. The system especially incorporates a line selector (1) of which the relay changes call line to the second line (B) upon black-out, its dialing circuit (11) and call current supplying circuit (12) into the system phone. The circuit (12) separates call current into voice signal component and DC voltage component, and then supply the voltage to call circuit (5). This method also increases efficiency of the system phone.
|
