| 摘要 |
PURPOSE:To attain talking with an original subscriber during retention again at the end of talking by providing a calling device during talking between a subscriber and a main link to retend an opposite subscriber during the talking and attain talking with the other subscriber not by hooking off but by dialing. CONSTITUTION:When a service subscriber 1 hooks off its handset to talk with other subscriber SUBC during talking with a subscriber SUBB, this hooking signal is detected by a hooking and cut off detection control circuit 12 via a subscriber supervisory circuit 11. When an output signal for detecting hooking is supplied from the control circuit 12, a switching control circuit 14 changes over a channel switching circuit 13, resulting that the 1st terminal is retended and the service subscriber 1 is connected to the 2nd terminal 4. When the subscriber SUBB listens to a DT tone, it dials to call the subscriber SUBC, and when the subscriber SUBC responds to it, the talking is attained with the subscriber SUBA through a path of the subscriber supervisory circuit 11, the channel switching circuit 13, the 1st terminal supervisory circuit 15, the 1st terminal 3, a main link 5 and an outgoing trunk 7. |
