| 摘要 |
PURPOSE:To realize the individual calling of an ordering system using a digital transmission line with small size and economy and to attain the use of a specified convolution code in place of a PN code, by transmitting a dial signal according to the presence/absence of the PN signal. CONSTITUTION:A voice output circuit and a digital encoder 11 and a digital decoder and a voice input circuit 15 are connected with a digital transmission line 14, the output of a dial signal encoder 2 switches an output of the voice output circuit and the digital encoder 11, and the output of a PN generating circuit 12 by using a gate circuit 13 at the transmission side, and transmits the PN signal to the digital transmission line in response to the dial signal. Further, a PN receiving circuit 16 detects the presence of the PN signal at the receiving side and gives an output to a dial signal decoder 10. The PN generating circuit 12, the gate circuit 13 and the PN receiving circuit 16 are all simple digital circuits in this case. |
