How early did the Great Northern begin installing electronic signals at grade crossings? I’ve seen them in 1958 photos, but am sure there were earlier ones.
It would use basically the same technology as block signals would, and I think they’ve been around since the 1910’s. I suspect they probably started to become common when highspeed trains like the Zephyr started to be developed in the thirties…though they maybe weren’t common until into the fifties.
“Electronic” is hardly the proper term, since the systems that were pretty widespread by the late 1930’s (thanks to a Roosevelt-era program to protect and/or eliminate grade crossings) relied on massive encapsulated relays to detect the short between the rails caused by the presence of a piece of rolling stock. As wjstix said above, they used the same detection system used by automatic block signals.
A gentleman who retired from signal maintenance on the Boston and Albany told me that it took two big flat files connected by a hefty chunk of cable to create a test short. The track speeder couldn’t, because it had insulated wheels.
Chuck
apparently the confusion here is about what it means for something to be “electronic.” electrical detection of trains and electrical actuation of signals dates back to the very late nineteenth century, but electronic enhancements to grade crossing signals began only about twenty years ago.
the grade crossing signals you saw in pictures of the Great Northern from 1958 are actuated by electrical track detection circuits that have been in use since about 1915; however, there is nothing “electronic” at all about such a circuit. The electric track circuit in use in 1958 (and, in most places, still today) uses a battery and charger, detection relay, and heavy duty wiring, but no electronic devices.
the most common tool used by signal maintainers to create a short circuit across the rails for test purposes is a “booster cable” of the type available in auto parts stores.
electronic devices have been added to grade crossing signals over about the last 15-20 years, and usually apply to two areas of the signal system.
- An electronic device is now commonly used in urban settings where a train must sit still in close proximity to a grade crossing, perhaps for hours or days. in the old days, such a crossing was controlled by a human operator who knew when the train was about to move. in the late 1970s, railroads began to install a doppler effect device with complex electronic circuits that can detect not only THAT a train is on the signal block, but WHETHER the train is moving or stationary, and, if it is moving, whether toward or away from the grade crossing.
Thus, without a human operator, the signal can be relied upon to clear when the train is sitting still, even if it is only 10 feet from the crossing, and to operate if the train moves toward the crossing, even if only a few inches.
- Recently, grade crossing signals have become available that include strobe lights, moving arrows, “time remaining” indicators, and other electronic enhance
Electronics vs Electrical. When I was in collage I learned that “electronics” is electrons moveing through space, as in a vacuum tubes, and “electrical” is electrons moving through wires and contacts. Of course I went to school just about the time transistors were being invented, and now I consider solid state devices to be electronic as well. I am not disagreeing with any previous posts, but I was remended of a cute lesson from my school days and thought I would share it. Now I hear the word electronical being used frequently and I am so confused…
Paul
Dayton and Mad River RR
Paul,
I remember the same lesson you did, from my high school electronics elective. By the time I took electronics courses in the mid-80’s, solid state devices were well established.
As for ‘electronical,’ that’s almost certainly a product of the same technologically challenged media morons who inflicted ‘nucular’ on the public consciousness and insist on the pronunciation He-ROW-shee-muh for the city that the natives (and knowledgeable Japanophones) pronounce He-ro-SHE-ma.
Chuck (who has studied nuclear safety)