| 摘要 |
PCT No. PCT/JP93/00123 Sec. 371 Date Oct. 4, 1993 Sec. 102(e) Date Oct. 4, 1993 PCT Filed Feb. 2, 1993 PCT Pub. No. WO93/15577 PCT Pub. Date Aug. 5, 1993.In a fire alarm system one of a fire receiver and terminal devices transmits the same signals in opposite transmission directions to first and second loop-signal lines. The remaining ones of the fire receiver and terminal devices receive the signals transmitted through the first and second loop-signal lines and detect whether there is an abnormality in transmission by detecting differences in the receiving times of the signals. Consequently, an abnormality of transmission is detected immediately. A fire receiver or terminal device which detects any abnormality immediately causes the first and second loop-signal lines connected with each other to form a signal loop-back path, thereby transmitting signals to the entire loop-signal line except to the position where the abnormality occurs. As a result, the reliability of signal transmission is significantly improved.
|
