| 摘要 |
PURPOSE:To indicate visually the extension busy easily by transmitting extension busy information to a visual indicating means through a channel switch and a subscriber's circuit. CONSTITUTION:A digital subscriber's circuit 103 is provided with a channel interface circuit 105 and a control circuit 104 and is connected between a time division channel switch 102 and a digital extension telephone set 106. Meanwhile, a channel interface circuit 101 which transmits extension busy information to the subscriber's circuit 103 through the channel switch 102 is connected to a central controller 100. When detecting call or release of the extension telephone set 106, the central controller 100 transmits extension busy information through the channel interface circuit 10, an extension busy information channel of the channel switch 102, and the channel interface circuit 105. Thus, the control circuit 104 displays extension busy information on an extension busy information display device 107. |
