| 摘要 |
PURPOSE:To make duplex operation possible in terms of broad-band signals by subtracting a transmitted signal from a signal received from a two-wire transmission line and then by sampling the obtained signal with sampling pulses differing from those of the transmitted signal. CONSTITUTION:A transmitted signal from four-wire transmitter 11 is made into an unbalanced signal by four-wire interface 13 and sampling circuit 14 converts it into a signal a PAM waveform, which is converted into an unbalanced signal by differential amplifying circuit 15. Further, it is sent to two-wire transmission line 19 by way of two-wire interface 16 and line terminating circuit 17. A received signal on which the transmitted signal of two-wire transmission line 19 has been superposed is sent to subtracting circuit 23, which subtracts a transmitted signal from interface circuit 16 from the input and sends its output to sampling circuit 26 via low-pass filter 25. Then circuit 26 samples the input with pulses of circuit 14 and interleaved pulses and interface circuit 29 obtains the unbalanced signal of it, which is supplied as a received signal to transmitter 11. |
