| 摘要 |
PURPOSE:To prevent trunk line from being interrupted even if the line switched to the interphone mode during a call, by bringing automatically the mode to the trunk line holding mode, when the line switched to the interphone mode during the call. CONSTITUTION:When interphone mode is used during a call, this data is fetched in a control section 10, which retrieves whether or not a data representing the duration of call is stored in a memory. Since information on the presence of an incoming call is stored, the control section 10 brings the telephone set to the interphone mode and the trunk line during the call to the trunk line holding state. Then, the communication to the trunk line during holding is attained by any telephone set. |
