| 摘要 |
The auto hold releasing circuit protects the hold call from the instantaneous line voltage variation and releases the call only when the hand set of a telephone connected to the call holding telephone in parallel. The circuit includes a hold switch (SW11) for generating hold instruction, a line voltage checker connected between the lines (L1,L2) for connecting a path controller and a communication circuit (22), a CPU (20) for holding the current path according to the hold insturction and for generating hold control signal to release the hold when line voltage decreases constantly during a fixed time, and a diode (D11) for providing path for transmitting the hold control signal to the path controller (23).
|
