| 摘要 |
PURPOSE:To realize a sending-back test in online mode through a half-duplex communication transmitter which allows full-duplex communication, by forming a return path in response to a carrier detecting signal from a demodulating circuit and a signal which is not being transmitted from a transmitting circuit. CONSTITUTION:To transmit and receive a normal data signal between a master station 20 and a subordinate station on half-duplex communication basis, the switch 26 of the master station 20 is placed at the side of a transmitting circuit 24, and the switch of the subordinate station 21 is placed at the side of a transmitting circuit 35. For a sending-back test by the master station 20 a data signal from the transmitting circuit 24 of the master station 20 after its carrier signal is modulated by a modulating circuit 25 is inputted through a down transmission line 22 to the demodulating circuit 33 of the subordinate station and while its demodulated signal is outputted to a receiving circuit 34, a carrier detecting signal is inputted to an AND circuit 40; since no signal is being transmitted from the transmitting circuit 35, so the AND circuit 40 generates an output to change over the switch 37, and the output of the transmitting circuit 35 of the subordinate station is sent back from a modulating circuit 36 to make a comparison between the transmitted and received data through the comparing circuit 29 of the master station. |
