| 摘要 |
PURPOSE:To recognize the presence of a visitor or the like even during a busy external line by allowing a control circuit to send an interruption signal to a telephone set while talking with an external line when a call signal comes from a door phone during the talking with external line. CONSTITUTION:When a visitor comes during the talking with an external line and a call signal from a door phone 13 from the visitor or the like is received by a control circuit 16, the control circuit 16 connects an interruption signal oscillator 23 to a telephone set 12 during talking with an external line to send an interruption signal to the telephone set 12. When the telephone set 12 holds the external line, the telephone set 12 talks with the door phone 13 and the external line talking is restarted by releasing the external line holding.
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