Are trains still detected in a block by their conducting/passing current between the two rails?
If so, do welded rails have an intentional electrical open/break where two blocks meet?
Perry BabinAre trains still detected in a block by their conducting/passing current between the two rails? If so, do welded rails have an intentional electrical open/break where two blocks meet?
Track circuits are electrical circuits with the steel wheels & axles closing the circuit.
There are specific Insulated Joints installed to facilitate the proper operation of Signals, Road Crossing Protection as well as various inspection detectors. Where stick rail is in use in signalled territory, it has wire bond wires welded to the outside of the ball of the rail at rail joints to insure proper electrical continuity, not depending upon the joint of the angle bars and bolts holding the joint together to be the path of electrical continuity.
Never too old to have a happy childhood!
Some light equipment is made with active current across the rail wheelsets to ensure the effect of 'continuity' even with poor contact between the rails. Note that in some cases, there can be a code modulation on top of the "electrical continuity" that carries information, and an active system needs to be able to amplify this correctly.
OvermodSome light equipment is made with active current across the wheels to ensure the effect of 'continuity' even with poor contact between the rails.
Most MofW equipment is designed so that it DOES NOT activate track circuit. MofW on track equipment does not operate on signal indication. MofW equipment operae on specific 'Track Car Authorities' that grant track occupancy between specific points on designated track(s) and for a specified time. The authority will also designate where the authorized MofW movement will change from one track to another.
A background ability of a 'Track Car Authority' if the person that received that authority is 'late' in reporting CLEAR of the authority, well beyond his authorized time limit - a train CAN be given authority to operate through the limits of the authority at Restricted Speed as a Search Party to find the overdue authority holder.
I was in a hi-rail that had a "shunt" switch.
rdamonI was in a hi-rail that had a "shunt" switch.
While that may be the case - I suspect its existence is to activate highway road crossing protection so that a hi-railer can get across an 8 lane road crossing without taking an extended period of time 'flagging' his way across it.
Welcome aboard. Keep the questions coming.
In addition to the signal indication (shunted rail = occupied rail) consider this.
A broken rail will mess all this up. Thus a broken rail, danger to travel over, will call out the signal maintainer to walk the rail and find the broken rail/circuit. endmrw0411231849
Cotton Belt MP104Welcome aboard. Keep the questions coming. In addition to the signal indication (shunted rail = occupied rail) consider this. A broken rail will mess all this up. Thus a broken rail, danger to travel over, will call out the signal maintainer to walk the rail and find the broken rail/circuit. endmrw0411231849
A broken rail (or broken bond wire in jointed rail) will cause a loss of continuity in one aspect of the electrical circuits that control track occupany indications. Occasionally a rail or bond wire will break on its own. Much more frequently those conditions will happen with the passage of a a train - one has to assume that the rail broke under the traffic of the train. When such is the case, from a Dispatchers point of view, they will see a train that has passed beyond the subject track occupany segment - and the segment stays lighted on the Dispatchers model board. Depending on local policy - signal inspector and/or MofW inspectors may be called, individually or collectively.
Aaaand, to throw a curve into the discussion, some railroads coded a signal on the tracks, so not only did the trackside signals operate as discussed, but a train on those tracks (with the proper equipment) could display the next signal aspect right in the cab...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
I'm sure Jeff has seen these a dozen times or so. Can't find videos for any other RRs off hand quickly.
https://youtu.be/Om9Wm2Dfm-s
https://youtu.be/z-iuEwp1AbA
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
Just to confuse things a bit... transit industry uses jointless track circuits using radio frequency.
Next Generation Track Circuits - Federal Railroad Administration https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/17934/Next%20Generation%20Track%20Circuits.pdf
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmannd Just to confuse things a bit... transit industry uses jointless track circuits using radio frequency.
I can believe audio frequency, but have a hard time believing radio frequency unless it is in the VLF range (3-30kHz) or lower end of the LF range (30 to 300kHz). Main reason for the disbelief is shunt capacitance.
No reference at all in the DOT/FRA Next Generation Track Circuits to RF or even high AF through the rails. US&S MicroLoc and MicroTrax don't appear to have a RF component; their technical support is at (800) 252-7276 and email railteam@switch.com if anyone wants to check current details (no pun intended).
The "transit" system appears to be operating at 1kHz, with transmitter power around 25-30W (according to GO Transit RC-0506-03SIG-01, October 2019) but I think that even though it references transponder height 6" above TOR, the system is using fixed-location receive coils, not RF on the track.
I don't think an ultrasonic (HSR IDEA project 42) system can be made projective for any great distance, let alone the 1-2 miles needed for safe braking between trains. I was interested in the TDR approach (HSR IDEA project 38) which would involve injecting a structured pulse into the track and reading any reflected signal -- the signal might qualify as "RF" in its internal modulation -- but as noted it only works if very accurate GPS/GIS data is overlaid on the readings.
oltmannd Just to confuse things a bit... transit industry uses jointless track circuits using radio frequency. Next Generation Track Circuits - Federal Railroad Administration https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/17934/Next%20Generation%20Track%20Circuits.pdf
Most, if not all on the main lines, have jointless circuits for crossing signals. Block signals still have the insulated joints.
Yeah Zug, I've seen those. I'd have to dig through some boxes, but I believe I still have my VHS tapes covering safety items such as cab signals. They were in the large training packet I received when going into engine service.
Now the cab signals, ACS and ATC, are history. Our area was discontinued last June, the rest of the system a couple months or so back. Now what do I do with all the old cab signal seals and cab signal test cards?
Jeff
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