| 摘要 |
PROBLEM TO BE SOLVED: To enable a terminal device of a network, to which plural terminal devices are connected by a data transmission line based upon IEEE 1394, to transmit and receive light signals by using a space as a medium. SOLUTION: Two series of signals from a twisted pair cable 17 with a feeder are converted by a code converting circuit 14 into an electric signal of one series, which is converted into an optical signal and radiated to the space by an optical transmission part 15. Optical signals transmitted through the space are received by an optical reception part 16 and converted into electric signals. The code converting circuit 14 having received the converted electric signal of one series converts it into signals of two series and sends them out to a twisted pair cable 17 with a feeder. Further, the electric signal from the optical reception part 16 is inputted to a cutoff and insertion/extraction detecting circuit 13, which detects whether or not there is an optical signal and whether or not a received signal is a reflected signal to detect the disconnection of a communication path and the insertion or extraction of a signal line connected to an opposite optical transmitter receiver. The detection result is sent to a bias circuit 12 and when no optical signal is received, the application of a bias voltage to the twisted cable 17 is stopped. |
