| 摘要 |
<p>PROTECTIVE DEVICE FOR RAILROAD SIGNALING APPARATUS The receiver of an audio frequency (AF) track circuit for a track section of an electric propulsion railroad is coupled across an associated impedance bond by the primary and secondary windings of a saturable transformer. The control winding of this transformer receives energy signals from a voltage comparator network which compares input signals from two pick up coils, one positioned in inductive relationship with each rail at the receiver end of the section. These coils are tuned to respond to a selected ripple characteristic of the rectified DC propulsion energy, e. g., the sixth harmonic of the basic AC power supply source. When the propulsion currents, and particularly the selected ripple characteristic, in the two rails are unequal, due to a broken rail, intervening ground, or other fault condition, unequal input signals from the coils actuate an output from the comparator which energizes the control winding, thus saturating the transformer core to uncouple the primary and secondary windings to interrupt the coupling between impedance bond and track receiver to register and hold a section occupancy indication, a fail-safe condition.</p> |
