| 摘要 |
PURPOSE:To effectively utilize a radio wave and to reduce energy consumption of the system by controlling the transmission power of an alarm transmitter corresponding to the required range of communication. CONSTITUTION:Signal generators 2a-2f output a passage detection signal when a train approaches / passes, signal transmitters 3a-3f add own addresses to these passage detection signals and transmit these addresses as train passage signals by radio waves, and an alarm transmitter 1 receives these train passage signals and transmits an alarm signal so as to notify the approach of the train to workers. The alarm transmitter 1 distinguishes the signal transmitter according to address information in the response signal, stops the increase of the transmission power when receiving the response signals from all the signal transmitters 3a-3f within a designated supervisory range, and afterwards executes communication with the signal transmitters 3a-3f within the monitor range by the transmission power. Thus, the alarm transmitter 1 can execute communication by the irreducibly minimum transmission power to enable communication. |
