| 摘要 |
<p>Coils 8, 10 of a track circuit are magnetically coupled to rails 5a,5b and located between them such that sections 7a-b, 11a-b of each coil are adjacent to respective inward-facing portions of the rails. Signal generator 6 supplies the first coil with a varying voltage signal for receipt by signal receiver 9 associated with the second coil. The received signal is null or below a threshold when an axle 12 of vehicle 2 causes a short-circuit, thus indicating occupied state. A third coil 15 is magnetically coupled to the rails and is coaxial to and surrounds the first coil such that sections 14a-b are adjacent to respective outward-facing portions of the rails. A second signal generator 13 supplies a varying current modulated with FSK technique on the basis of a modulation code (CODE), thus transmitting signalling information to a detector on the train.</p> |
