| 摘要 |
PURPOSE:To surely detect a fault of a travelling instrument by measuring the length of a transmission time of a radio section and recognizing it as a fault of the travelling instrument when the length of the transmission time exceeds a prescribed range. CONSTITUTION:An AND circuit 21 ANDs a clock pulse and a transmission power on/off signal and sends a clock pulse when the transmission power on/off signal is logical 1 to a counter 23. The counter 23 counts up the inputted clock pulse number. A comparator circuit 25 receives a count N1 of the counter 23 corresponding to the transmission time length and compares it with a prescribed value C corresponding to a normal transmission time length and outputs logical 1 when the conditions of N1>C, N1=C, N1<C are established to 3 ports of N1>C, N1=C, N1<C. Whether or not the transmission time length is faulty is detected by detecting whether or not logic '1' is outputted to the port of N1>C. The frequency of the clock pulse depends on the measurement accuracy of the transmission time length to be measured. Thus, the fault of the travelling instrument is surely detected and the transmission of an undersired radio wave is prevented. |
