| 摘要 |
PURPOSE:To make a signal transmitting and receiving circuit, which is provided in a main device, signal, by communicating a control signal between the main device and a key telephone set in time division. CONSTITUTION:When the handset is hooked off and a trunk line CO-j is designated by a line button LK-i, the line button LK-i and a hook switch HS-i are operated, and a signal generated by these operation is inputted to a control circuit KCC-i. If the trunk line CO-j is idle, the circuit KCC-i outputs the request signal for call to a signal transmitted and receiving circuit KCLI-i to transmit the request signal to a main device ME. In the main device ME, this request signal is inputted to a control circuit MCC. Thus, a channel switch circuit SW is controlled to connect a service line SP-i from a key telephone set KT-i and the trunk line CO-j. Further, required control signals are used to realize functions of trunk line incoming, extension service, holding, transfer tripartite call, etc. |
