| 摘要 |
PROBLEM TO BE SOLVED: To enable high detection accuracy, even if a train travels at low speed, by detecting a time difference from reception of a radio signal till listening to a sound wave and calculating an absolute position of the train based on positional information of the radio signal according to this time difference. SOLUTION: An on-vehicle device 30 is connected with an automatic train stopping device 40 via a prescribed signal line and an absolute position calculating means is constituted of this on-vehicle device 30. For instance, a sound wave listening interruption signal is introduced into an on-vehicle processing part by listening to a sound wave S2 when this sound wave S2 comes in a sound wave receiver behind a radio signal S1. An isolating distance D with a ground device 20 at a present point of time is calculated. This isolating distance D is added to positional information on an installation position of the ground device 20 and a present position P of a train TR is determined. At this time, because the installation position of the ground device 20 is a preliminarily fixed value, the finally obtained present position P of the train TR can be specified as an absolute position of the train TR in the railway line.
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