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US 4,172,576 AGranted
Highway crossing system with motion detecting apparatus
AssigneeGeneral Signal Corporation
InventorsFrank A. Svet, Jr., John W. Parker
Life of this patent
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AssigneeGeneral Signal Corporation
InventorsFrank A. Svet, Jr., John W. Parker
Estimating the term…
A highway crossing warning system includes a motion detector transmitter and receiver respectively coupled to the track rails adjacent the highway crossing for detecting motion of an approaching train. Wrap-around approach sections initiate operation of the highway crossing warning, but once motion is detected, the motion detector can serve to inhibit the highway crossing warning, after a predetermined delay, if motion indication ceases. To increase the effectiveness of the motion detector, the motion detector transmitter impresses a modulated carrier onto the track rails, wherein the modulation is phase locked to the carrier. The receiver, tuned to the carrier frequency, detects the modulation, and then determines from the level of the modulated signal whether or not approaching motion is detected. The transmitter employs solid state circuits switched between saturated and off conditions to prevent circuit component failures from masking approach motion. The ring sustain time period is arranged to provide a minimum constant warning time regardless of changes in train velocity, so long as train velocity is maintained above a predetermined threshold within a predetermined distance from the crossing.
In a highway crossing system for warning highway traffic of the approach of a railroad vehicle, which system includes a railway vehicle motion detector, an improved transmitter for said motion detector including:
A highway crossing warning system for warning highway traffic of the approach of a railroad vehicle including a railway vehicle motion detector having a receiver and transmitter, said transmitter including:
In a highway crossing system for warning highway traffic of the approach of a railroad vehicle, which system includes a motion detector, an improved transmitter arranged to prevent circuit failures from increasing amplifier output comprising:
An improved motion detector for a highway crossing system in which a modulated signal is transmitted in track rails adjacent said crossing and a received demodulated signal is processed to detect approaching motion, said improved motion detector preventing potential unsafe failures and including:
Dependencies are inferred from the claim text.