| 摘要 |
PURPOSE:To make trunk-line holding operation in off-hook operation ineffective by providing an off-hook judging means which judges whether plural key telephone sets connected to a main equipment are in off-hook states or not and making the holding of a trunk line ineffective when the key telephone sets are judged not in the off-hook states. CONSTITUTION:Whe the hold key of telephone set connected to the trunk line is operated during on-hook dialing or public-address reception in the on-hook state, a control circuit CTm receives hold key operation data and collates it with the information in a memory to confirm whether a relay L is restored or not. Thus, whether the trunk line is acquired or not is judged and whether the telephone set connected to the trunk line is in the off-hook state or not is judged by collation with the information in the memory. When the telephone set is ready for a calling state, relays HL and L are controlled to hold the trunk line, and control data is transmitted to the telephone set to disconnect a talking circuit TKC from a talking line LT; and then control data is transmitted to telephone sets TEL1- TELn to flicker the trunk line pilot lamp individually. |
