| 摘要 |
PROBLEM TO BE SOLVED: To perform the proper monitoring in response to the moving state of a slave unit by allowing a master unit to change a detection cycle according to the field intensity of the answer signal received from the slave unit or the changed variable of field intensity of the signal that is transmitted from the master unit and then received by the slave unit. SOLUTION: The count number N of a counter 14 is reset and a 1st timer 8 is started. A master unit 1 transmits and receives signals to and from a slave unit 2 when a 1st set time, i.e., a time cycle that is set by the timer 8 elapsed and detects the field intensity of the received signals to read the field intensity data D1. When the difference between the detected data D1 and the reference data exceeds the threshold S, the count number N of the counter 14 is increased up to 1. When the preceding field intensity data D2 are available, the data D2 are compared with the data D1. When the difference of both data exceeds the threshold S, the count value N of the counter 14 is increased up to 1. When the count number N does not exceed the set frequency C, a 2nd timer 9 is started. The set time of the timer 9 is shorter than the 1st set time.
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