| 摘要 |
PURPOSE:To simplify the circuit constitution and then decrease the core number of the wiring cable, by varying the call current of the telephone line via the constant current circuit within the slave unit and then identifying the button selection, the holding and the dial information via the detecting circuit within the master unit. CONSTITUTION:The connection is secured between slave units #1-#3 and the master unit of the key telephone equipment via power lines +P and -G, call line T and information line J each. Then serial-parallel converting circuit 23 which converts the serial information into the parallel information is provided to units #1-#3 along with call current control circuit 21 which controls the value of the call current to the level corresponding to the operation state of the level set previously and with operation of the key. On the other hand, slave unit detecting circuits 8-1-8-3 which identify the valve of the call current through a comparison with the reference level set previously are provided to the master unit along with parallel-serial converting circuit 14 which converts the parallel information into the serial information. Then the call current flowing to line T is varied by circuit 21 within units #1-#3, and the button selection, the holding and the dial information are identified through circuits 8-1-8-3 within the master unit. In such way, the circuit constitution can be simplified. |
