| 摘要 |
PURPOSE:To enable to recognize reply of a remote telephone subscriber by adding reply indicating tone by output of a polarity inversion detecting section and a polarity inversion detecting section having the same input with a monitoring circuit. CONSTITUTION:At first, a telephone circuit 1 is connected to a monitoring circuit 7 by bringing down a circuit change-over switch 2 and a change-over switch 5 to lower side in the figure and audible sound of 400Hz received from the circuit is generated in the circuit 7. Then, the switch 5 is changed to upper side, and the circuit 1 is connected to an automatic dialing section 6, and dial transmission is performed. After completion of the transmission, the switch 5 is changed again to lower side to connect the circuit 1 to the monitoring circuit 7. Consequently, audible sound modulated by 16Hz received from the circuit 1 is generated from the circuit 7. When the object of telephone makes a reply, the ringing tone is stopped, and at the same time, DC loop polarity of the circuit 1 is inverted, and accordingly, the polarity inversion detecting section 8 starts to operate a reply indicating sound generating circuit 9, and reply indicating sound is generated from the circuit 9. |
