| 摘要 |
PURPOSE:To allow an electronic computer to detect instantly a line disconnection and a busy state of an opposite terminal, by detecting a call tone or a busy tone generated when the line under connection is interrupted in an on-line system via the telephone line. CONSTITUTION:A telephone terminal device 1 and the electronic computer 4 are connected via a telephone network 2 and a voice response device 100, and when the device 100 receives an incoming signal from a terminal 1 via the telephone network 2, a telephone subscriber circuit 3 reports it to the computer 4 and the channel is connected with the command of the computer 4. When the line is disconnected, a call tone outputted from the telephone network 2 is received at a frequency receiver 5, the tone is compared with a simulated dial tone generated from a tone forming circuit at a comparison circuit 7, and the computer 4 detects the disconnection of line by setting a flag from a flag generator 8. The detection of a busy tone is detected similarly in comparison with the simulated tone from the tone generating circuit 6 and the setting of a flag. |
