| 摘要 |
PURPOSE:To attain an interphone set with higher publicity and high efficiency by providing a timer means limiting an external call time so as to prevent an external talking line by a specific housing master set from being occupied. CONSTITUTION:A hook-up signal is transmitted to a common gate equipment via a call line at point of time of hook-up of a call destination, causing to allow the common gate equipment to start measuring a call time, and when the time reaches a prescribed call time, even if the called party is in the state of hook- up, the external call is interrupted forcibly. The common gate equipment M in figure is provided with a timer 37 controlled by a CPU11. The timer 37 is constituted as, e.g., a one-shot timer, and started when the CPU11 discriminates an external call and an external talking line is formed, and transmits a timeup signal to the CPU11 when a fixed time, e.g., 3min is elapsed. Even if the external call is not finished yet, the CPU11 interrupts forcibly the external talking line in this case. |
