| 摘要 |
PURPOSE:To attain prevention of noise of an exchange system with a simple element by inserting a gate circuit to an input side of a talking line converting circuit of the PCM side of a PCM-FDM converter, and allowing exchange information to turn off a gate circuit to interrupt the talking converting circuit system. CONSTITUTION:A dial pulse attended with the calling of a telephone system is transmitted to a signal generator 17 via a signal selecting circuit 13 and also transmitted to a guard timer 26 via an E lead and interrupts equivalently a channel 22 of the own station side by turning off a channel system NAND gate 28 via an OR gate. On the other hand, a response signal of an opposite exchange is detected by a demodulator 20 and a signal detecting circuit 14, inputted to a guard timer 27 via an M lead, a timer signal of a prescribed time is generated, the NAND gate 28 is turned off via the OR gate to interrupt the channel 22 of the own station side. Thus, the change system noise generated by a dial pulse is eliminated from the channel through the simple circuit constitution. |
