| 摘要 |
PURPOSE:To realize transfer calling and link calling functions with simple constitution by providing a switch method that interrupts the DC loop of a telephone set and by putting the tone ringer of the branch connection telephone set into operation by driving the switch method. CONSTITUTION:As incoming arrives from an office, tone ringer 2 is put into operation by the call signal and then a normal telephone call can be made with the handset off the hook. Next, hook switch HS is made, and consequently the DC voltage applied between main wires L1 and L2 is charged in capacitor C by way of bridge rectifier D and resistacnce R. To transfer the call from an engaged telephone set to another telephone set connected in parallel, the caller depresses S1 and S2 to feed electric current to multivibrator MV, which oscillates. As a result, relay A performs interrupting operation and the tone ringer of the telephone set operates. The simple constitution like this provides transfer calling and link calling functions. |
