| 摘要 |
PURPOSE:To perform high-reliability detection over effective electric power operation, by arranging a previous signal, composed of a specific code string, at the head part of an information word string in each group. CONSTITUTION:A wave to be modulated which is received by an antenna is demodulated by receiver 22 and then converted by waveform shaping circuit 23 into a digital signal, which is sent to decoding and controlling circuit 24. Circuit 24 controls switching circuit 26 to switch battery 27 which supplies power to receiver 22 and circuit 23. On detecting a preamble signal, said controlling circuit 24 turns on circuit 26 at any time for bit synchronization. If a block synchronizing signal is detected in this state, circuit 26 is turned off normally to exclude the power supply to respective parts except circuit 24. Thus, circuit 26 is turned on normally at the time of a corresponding group to supply the power to respective parts. In the starting of the power source, the receiver waits for the starting of the power source by using a previous signal consisting of logic ''1'' and ''0'' and also detects an information work, thereby sending it to alarm horn 29. |
