When a track circuit shows occupancy during testing, what would you expect the detector to indicate?

When a track circuit shows occupancy during testing, what would you expect the detector to indicate?

• A. The detector would indicate clear and permit normal track movement.
• B. The interlocking state would be unaffected.
• C. The corresponding detector would indicate occupied or change the signal to restrict movements in that block.
• D. The detector would show a fault alarm and stop the system.

Answer: (C)

Track circuits report whether a block is clear or occupied, and the detector for that block mirrors that status. When occupancy is detected during testing, the detector should indicate that the block is occupied, and the interlocking logic will respond by restricting movements in that block (typically by presenting a red signal or otherwise preventing routes into that block). This is how safe operation is maintained: the presence in the block is communicated to the signal system so trains aren’t allowed into a space that isn’t clear. A fault alarm would come only from a detected fault, not from normal occupancy. So the expected result is an occupied indication from the detector, with the system taking appropriate action to restrict movement.

Track circuits report whether a block is clear or occupied, and the detector for that block mirrors that status. When occupancy is detected during testing, the detector should indicate that the block is occupied, and the interlocking logic will respond by restricting movements in that block (typically by presenting a red signal or otherwise preventing routes into that block). This is how safe operation is maintained: the presence in the block is communicated to the signal system so trains aren’t allowed into a space that isn’t clear. A fault alarm would come only from a detected fault, not from normal occupancy. So the expected result is an occupied indication from the detector, with the system taking appropriate action to restrict movement.