| 摘要 |
It is enabled to perform the location confirmation as precisely as possible at a small number of receiving stations. In the respective stations, after performing the operation of filtering and amplifying at the front end portion, the signal passes through the discriminating portion corresponding to the transmission signal from the transmitter. Thereafter, the electric power or amplitude of the signal emitted from each transmitter is measured. The measured value is sent to the central station through the backbone communication network. The more the transmission distance of the electric wave is, the more the electric wave attenuates. Consequently, it is possible to know the zone in which the worker carrying the transmitter is staying nearby by respectively comparing with each other the electric powers of the respective signals; a, b, and c transmitted from the transmitters a-c measured by the respective receivers. The transmitters generating the specific signals respectively are given to the respective workers, and it is possible to estimate the zone in which the worker is staying and to confirm the location of the worker by giving the receiver in each zone a function of discriminating all of those signals from the others.
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