| 摘要 |
PURPOSE:To simplify the circuit constitution by installing the main wire and extension detecting circuits to the master unit of the key telephone equipment and thus detecting the current change caused by the dial operation through each main wire detecting circuit. CONSTITUTION:Call current control circuit 21 connected to the dial contact is installed to channel T of slave units #1-#3 each of the key telephone equipment in which the call current system is separated from main wires 1 and 2 each in the DC way. And cross-point circuits 6-1, 6-2 and 7 possessing cross-point SCR each are provided among trunks 2-1 and 2-2 of wires 1 and 2, extension trunk 3 and units #1-#3 each. Furthermore, main wire detecting circuits 2-1-2 and 2-2-2 plus extension detecting circuit 3-2 are installed to trunks 2-1 and 2-2 plus trunk 3 each in order to detect the current change caused by the dial operation. And main wire control circuits 4-1 and 4-2 plus extension control circuit 5 are actuated with the detected output. Thus the channel corresponding to the dial pulse is formed. |
