| 摘要 |
PURPOSE:To freely make a mode change from an off-hook telephone call to an on-hook telephone call by changing a key telephone set from the off-hook telephone call state to the oh-hook state in response to the on-hook operation of the by telephone set on which a line button is operated before a timer enters a time-up state. CONSTITUTION:When one key telephone set ST 4 is put in on-hook operation, its operation data is received by a CPU 14, buttons in a KB 37 are operated similarly, and a CPU 14 controls a TSW 12 to make an exchange connection. Then when line wire origination is performed, dial origination is performed under the control of a selected LIF 11 and when extension origination is performed, an extension ring-back tone is sent out under the control of a DP 36 to the ST 4 on the opposite side, so that a telephone call state is entered when the opposite side answers. Further, incoming signals from line wires 21-2n are detected by LIFs 111-11n and the CPU 14 controls the DP 36 of the respective STs 41-4m to send out a line wire incoming ringing tone, so when one ST 4 answers by off-hook operation, the CPU 14 controls a TSW 12 to connect a channel.
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