| 摘要 |
PURPOSE:To detect a carrier sense signal within the conventional detecting time for carrier sense signal set with use of a coaxial cable by providing a packet data return switch into a transceiver and controlling this switch with the detecting signal received from a means which detects the presence or absence of the signal sent from a device set at the network side. CONSTITUTION:A return switch 19 is connected to the output line of a transmission line receiver 11 of a transceiver 4 and the output side of the switch 19 is connected to the input terminal of an OR gate 20. Thus the ON/OFF states of the switch 19 are controlled via an optical power detecting part. A network side controller 7 includes an optical power detecting part 26 which supplies the output of a light receiving part 21 and a signal cutting part which prevents the transmission of signals to a light transmitting part 24 from a transmission signal selecting part 23 in case the part 26 detects no optical power. In such a constitution, the packet data received from a terminal 1 is returned within the transceiver 4 without passing through the optical fibers 5 and 6 and sent back to the terminal 1 again. Thus the carrier sense signal detecting time T has no relation with the lengths of both fibers 5 and 6. |
