| 摘要 |
PURPOSE:To realize three-party talking with an office telephone set by providing the office telephone set with an indicator to react to a secret number, etc. from a calling telephone set or called telephone set and also using a telephone transfer unit to allow the said telephone to communicate with the calling or called telephone. CONSTITUTION:When a calling telephone A is talking with a telephone E via the lines 12 and 11 and if it is desired that an office F participates in this talking, the telephone A or E sends a secret number using a PB tone generator 30 and the signal is discriminates by the signal discriminator and a indicator 5 is operated. When an office handset 6 is off-hooked, a CPU31 detects the off-hook and operates an analog switch circuit 25, and the signal from a line 11 is conveyed to the handset 6 and also the signal from a line 12 is conveyed to the handset 6. The signal from the handset 6 is conveyed to the lines 11 and 12 via two-wire four-wire separators 17 and 18.
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