| 摘要 |
PURPOSE:To adapt the signal transmitting system to the time division controlling system, by providing a holding key independent of an interlocking key for line selection and a relay contact which forms a holding loop temporarily together with the contact of said interlocking key. CONSTITUTION:In a telephone set 2, a line selecting key 9 and a hook switch 12 are closed and a service circuit 13 is connected to a trunk line 3 during the service to the trunk line 3. An LED 14 is lit continuously. When a holding key 15 is depressed, a holding relay 16 is driven, and its contact is operated to form a holding loop temporarily. Simultaneously, a holding signal is sent to a controlling circuit 18 through a controlling circuit 17 and a control line 6 and is decoded and detected to drive a holding relay 19 through a trunk line circuit 20, and its contact 7 is operated to form a holding loop of the trunk line 3. Thereafter, the contact 10 in the telephone set 2 is released, and the LED 14 displays holding. Thus, a key telephone device suitable for adapting the signal transmitting system between the telephone set 2 and a master device 1 to the time division controlling system. |
