| 摘要 |
A telephone connection is established between a pushbutton telephone set and one of telephone lines through a pushbutton telephone set unit, a speech highway, and a telephone line unit. When one of line and extension keys of the pushbutton telephone set is pressed by the user during the telephone connection, a CPU in a control unit determines whether the telephone connection is being made based on the period of time that has elapsed after the pushbutton telephone set has captured the telephone line. If the telephone connection is being made as determined by the CPU, then the CPU controls a time switch circuit according to hold function data stored in a RAM to connect the telephone line unit to a hold tone generator through the speech highway, thus holding the telephone connection. Thereafter, the CPU captures a telephone line corresponding to the depressed one of the line and extension keys.
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