| 摘要 |
PURPOSE:To sound-call a callee through a speaker built in a key telephone set during the calling from a calling side by detecting an additional dial signal determined beforehand from the calling side and closing a channel path from a private line to the key telephone set. CONSTITUTION:While the callee is called by an audible sound, when an additional dial determined beforehand is sent from the private line Lk, a dial signal detecting circuit 21k detects this, and through a dial signal deciding circuit 22, additional dial data are sent to a control circuit 50. By the data, the control part 50 sends the data to change from an audible sound calling to a sound calling through a data transmitting/receiving circuit 51 to a data interface circuit 31, closes the channel corresponding to the private line Lk of an interface circuit 23, controls a channel switch part 4 and links the private line Lk and the calling line of a key telephone set Ti. The circuit 31 controls the key telephone set Ti based upon the data sent from the control circuit 50 and changes over the speaker built in the Ti from an audible sound source to a calling line.
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