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DTMF Deactivate signs Prototype railroading
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Super User 6,008 posts Ken Rice Super User 6,008 posts
Ken Rice

About a month ago, before the recent unpleasantness started, I spent a few hours looking at every part of the Grafton and Upton RR visible from public property.  Looking back over some photos today I was reminded of something I'm curious about.  In two places I noticed blue signs with the text "DTMF DEACTIVATE" and a number like "*0001".  I believe DTMF is the dual tone multi frequency tones (like touch tone phone dialing) which I believe some railroad radios can send, so I assume the number is the number they need to send to deactivate something.  Since both signs are near grade crossings I'm guessing that's what they deactivate.  But what exactly does "deactivating" a grade crossing do, and why do they need to do it?

A couple crops of the signs so they're easy to read:

_cropped.JPG  _cropped.JPG 

The one on the left is at the CSX Interchange in North Grafton, right about here  https://goo.gl/maps/MP3NyjG55fsA6nAj7

The uncropped photo for more context.  There's a derail there to protect the main, and there's a grade crossing where the interchange track crosses Westoboro Rd.

IMG_1598.JPG 

The other sign is just about where the G&U goes under the Mass Pike, here:  https://goo.gl/maps/4JtFctdQrYfZJqFW8.  The uncropped photo for more context:

IMG_1608.JPG 

I was standing on Tracy Ann Dr to take the photo, that's a small road that doesn't have a crossing gate, just signs.  But a short distance in the other direction the G&U crosses Snow Rd - the road on the right in the above photo, which has shiny new crossing gates.

IMG_1610.JPG 

All these signs and crossing gates are new enough so they don't show up in the google street views.

Any thoughts on exactly why you'd want to deactivate a crossing gate from the locomotive?

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Russ Bellinis Prolific poster 3,335 posts
Russ Bellinis

Do those signs mark where the

traffic crossing signals deactivate when the last car on a train passes the grade crossing?
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Tim Bowser NCR-Boomer Frequent poster 557 posts
Tim Bowser NCR-Boomer

Distant Signal

Danny Harmon's YT videos, the latest one had DTMF being used on one of the CSX subdivisions to throw turnouts and derails remotely from the cab.  Your first photo shows a derail to the right of the sign, the second *might* be a turnout past the bridge(?).  "Deactivate" in this case would be to drop (deactivate) the derail.

Saves the conductor a heck of a walk in some situations...

Tim B.
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Ken Rice Super User 6,008 posts
Ken Rice

Derails and turnouts

Interesting Tim.  There’s no turnout or derail anywhere near the sign in the second photo - it’s at least a mile and a half to the nearest turnout heading south under the pike (the way the photo is facing).  If you open the photo that has the derail in it and zoom in a bit it looks to me like a typical hand thrown derail.  I’m not sure what a motorized derail mechanism looks like but I’m guessing it would look something like a remote switch motor.

Danny Harmon - is that the Distant Signal youtube channel?  I’ve got the latest one marked to watch after work, thanks!

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jeffshultz MRH Staff 8,226 posts
jeffshultz

Are they near switching areas?

I wonder if perhaps the grade crossing sensors are within the area where cars may be left during switching operations, so they would send tones in order to raise the gates if they weren't actually planning on crossing the street?

orange70.jpg
Jeff Shultz - MRH Technical Assistant
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David Husman dave1905 MRH Author 10,150 posts
David Husman dave1905

Derail

I am less inclined to think it controls the derail, since it appears the derail has a conventional hand operated switch stand.  If it were powered or dual control, I would expect it to have a different type of stand.  Now it might have an electric lock controlled by DTMF or possibly there is an electric lock on the main track switch.  

I also am squishy about activating crossing signals by DTMF, if the crew failed to act or fat fingered the number you could end up in the crossing with no signals or activating the signals late.  I could see deactivating signals, for example if the train stops near the crossing and you want to turn off the signals or bells because the train is going to be there a while.

Dave Husman

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Ken Rice Super User 6,008 posts
Ken Rice

Near switching area

The first one near the derail is one the interchange lead, right off the north end of the North Grafton yard.  Mostly they switch from the south end of the yard, but on occasion I think they do need to use the north lead a little.

The second one is half a mile south of the nearest switch to the north (a spur for Washington Mills), and a mile and a half from the switch to the south for a storage track in Grafton.

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jeffshultz MRH Staff 8,226 posts
jeffshultz

Right off the yard?

For the first one - would that be a good place for trains to sit as they wait for access to the yard? I could see having a crossing gate deactivation for that.

No idea on the second one.

orange70.jpg
Jeff Shultz - MRH Technical Assistant
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Ken Rice Super User 6,008 posts
Ken Rice

Right off the yard

That's the interchange lead with CSX, so that derail will only come off when CSX is picking up or dropping off interchange traffic for the G&U.  But yeah it might make sense that if they need to wait for a track to be cleared out or something.

Or I suppose if the grade crossing circuit activates when they just need to get an engine on the lead to run around something without actually crossing the street.  Here's a chunk of satellite photo that shows that grade crossing - the sign is on the north side of the street.

erchange.png 

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Backshophoss Regular poster 198 posts
Backshophoss

The DTMF tones turn on/offthe crossing lights

Cheaper to install/maintain then track circuits.and the "false trips" of the lights on due to a short in the track circuits.

Both G&U,CSX crews tone on or off the lights as needed
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Ken Rice Super User 6,008 posts
Ken Rice

Activate?

Thanks backshophoss, sounds like you’re in the know.  Given that until recently they had a guy driving around ahead of trains to flag crossings this DMTF approach is a big step up.  And now that I think about it given that it’s all older jointed rail on the second one and the cross gate is new I should have noticed new bond wires across the joints, but I didn’t.  Might have overlooked them over course, but no bond wires fits together with avoiding a track circuit.

On the other side of those signs (visible to the train when approaching the grade crossing) would there be something like “DTMF ACTIVATE *0000”?

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caniac Regular poster 312 posts
caniac

It's very unlikely the FRA

It's very unlikely the FRA and state UTC officials would approve a grade crossing system not primarily activated via an occupied track circuit. In fact, the odds are zero. Other items: 1) All radios operating on AAR channels utilize DTMF functionality. Ever hear a crew tone up a dispatcher? 2) There are no "sensors" in the track that detect trains in a crossing circuit. The approach and island use either DC track circuit, an AC-out/DC-back through a rectifier, or audio frequency AC signals to detect the presence and/or movement and speed of a train. As for the DTMF receiver at this particular location, it's mist likely used to override activation when a train is using the approach as a drill track. But the island circuit over which the road runs must by federal law be activated at all times when occupied, no overrides accepted.
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Tim Bowser NCR-Boomer Frequent poster 557 posts
Tim Bowser NCR-Boomer

About that Distant Signal

Clicking on the link takes you to Danny's description of how CSX "threw a bone to the neighborhood" with DTMF control of turnouts in this section of the territory:

 (11:50 seconds in)

Tim B.
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Ken Rice Super User 6,008 posts
Ken Rice

FRA, Distant Signal

Thanks Tim, I watched that- pretty neat.

Caniac- do you have any references for the FRA rules regarding crossings?  I would have thought they’d be OK with manually activated gates, since they’re clearly OK with no gates at all and manually flagging crossings.

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caniac Regular poster 312 posts
caniac

CFR 234 and practical

CFR 234 and practical experience. Gates or no gates make no difference. That's up to the municipality or taxing district that pays for the crossing installation and reimburses the railroad for material and maintenance. Yes, there are crossings that train crews can activate manually via DTMF. Never allowed on a main line (although there are mainline xings equipped with DTMF receivers for use only by hy-rails). Use on yard or other than main track only at restricted speed. And the DTMF is a secondary system. There will always be a track circuit or other means for primary activation of the crossing by the presence of a train.
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Ken Rice Super User 6,008 posts
Ken Rice

track circuit

This is a shortline, they never get up to class 1 mainline speeds.

You've made me very curious now, I want to go back and take another look at those grade crossings when I get a chance.  It's quite possible I overlooked evidence of a track circuit - I wasn't specifically looking for it at the time, and my photos aren't good enough to see bond wires across the rail joints.

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caniac Regular poster 312 posts
caniac

Appears to be insulated rail

Appears to be insulated rail joints in the photo with the crossing bungalow. Evidence very probably of a simple "island only" crossing. Crossing has to activate and remain activated with the island occupied by a loco or car shunting the track. DTMF cannot be used legally to override this. So the DTMF receiver, which has an internal relay, contact of which is used to pick up a crossing relay, could provide advance activation prior to a train reaching the island.
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Prof_Klyzlr Moderator 8,021 posts
Prof_Klyzlr

Reference?

Dear Caniac,

Quote:

 DTMF cannot be used legally to override this.

I appreciate that in a "FailSafe"/"Safeworking" headspace,
it's arguably safer to allow DTMF ENable than it is to allow DISable,

but If I may ask, do we have a reference for this?
- Specific RR GCOR ref?
- Specific RR local division/sub rules ref?
- NORAC ref?
- FRA ref?
- NTSB Ruling/ref?
- Safeworking Equipment Manuf ref?
- other?

Not attempting to be argumentative,
just would like to further my "Rule/Ref < -> Practical "in-the-field" observation" knowledge.

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS I wonder where "SignalMaintainer Paul" is,
he'd be just the guy to query/confirm about this, from a Pac NW BNSF standpoint...
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Backshophoss Regular poster 198 posts
Backshophoss

NMRX has a crossing at a station,they use DTMF tones

to drop the gates before leaving that station,the track circuit times out when a station stop is made.

yes NMRX does have approval for this.

The CSX side is the full setup with track circuits,the G&U sidin/ yard lead is beyond the CSX derail

that's a rod connnection to the mainline switch.Beyond the derail is G&U's track,in a yard no less.

figure it's FRA approved
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caniac Regular poster 312 posts
caniac

Certainly OK for that use,

Certainly OK for that use, 'cause it is not an override of the crossing circuit, it augements it. But any crew that tries to use it for any other purpose and an incident occurs, crossing recorders will nail them. Bye bye to the job.
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stevej New member 10 posts
stevej

remote control of level crossings

G'day, Until my transfer to Tasmania in 2004, I was aware of radio remote controlled turnouts, but had not experienced such. Most protected level crossings have two track circuits on approach, the advance and short. The advance circuit ensuring activation prior to train arrival when at speed. The short being additional to ensure activation, but primarily to deactivate protection on the opposite side when the train is clear. Should a train not activate protection at the advance circuit, it must stop and then slowly approach the short circuit to again stop. And wait until all road traffic has halted prior to continuing across the level crossing. Should the protection be a failure, the train must be flagged across the level crossing by a crewman. I doubt that slow speed short lines would possess both track circuits. However, a single circuit would need to be at a sufficient distance to activate the protection at regular train speed. That single circuit being at a longer distance from the crossing to the normal short circuit. The opposing circuit not deactivating the protection until the train is clear and being much longer than a short circuit. I would imagine at locations where shunting regularly occurs, and the train would hit the circuit, but not encroach on the crossing, a method of deactivation is necessary. Many motorists become impatient when encountering delays at level crossings and may take chances resulting in tragedy. One alteration here in NSW was the adoption of Predictor level crossing protection in the late 1990s. This being implemented at locations where vastly different train speed occurred, passenger versus freight. Upon hitting the advance circuit, the train speed is determined, and that factored into the timing of the protection. The express high speed pas running at 160 kph reaching that crossing much sooner than a slower freighter. Motorists whinging about the delay at such original level crossings while waiting for freighters and potentially taking chances. BUT, the location of some of these predictor circuits then posed operational restrictions upon heavy slow slogging freighters. These being where steep grades exist on approach to the actual level crossing. Prior to the implementation of the predictor circuits, a freighter could slog over the top of the hill through the original advance circuit. The let the train pick up speed on the down hill section to assist with climbing the hill on which the level crossing exists. BUT, this was banned as increasing train speed once past the advance circuit would not affect the timing. The freighter thereby reaching the level crossing earlier than the predictor circuit had factored time wise. Thusly, the freighter must apply the brakes to prevent speed increase and subsequently struggle up the following hill. I am also wondering if the remote deactivation is a facet of Quiet Zone level crossing type protection. Here the EPA regulations restrict the amount of noise being generated by the transport industry within built up areas. While I discovered that the radio remote turnout operation in Tassie worked well, I was slightly suspicious of an application to a specific level crossing. The Naval Road level crossing within the Hobart yard limits was protected by a track circuit and type F lights and bells. The actual circuit being only the short circuit not very far from this crossing. Hence a post with push button was positioned at a distance from the crossing on the right hand side of the track. Unlike the standard gauge and broad gauge railways Down-Under with left hand cabs, the narrow gauge mobs had right hand cabs. To depart the yard, or when shunting, the driver must lean out of the cab and hit this button to activate the protection. Miss that button and only the short circuit would then activate the protection providing very little time prior to arrival of the train. This situation was exacerbated by the oddity that rebuilt locos in Van Diemens Land were Left hand cab. This requiring the driver to jump up and dash across the cab to attempt to thump this button. While shunting, approach to the level crossing could occur very repetitively, but the train may not actually reach the crossing. Hence a time out facet existed to cancel the protection after a period if the train did not encroach the short circuit. It was eventually decided to apply remote radio control of this level crossing in conjunction to the push button. Thereby preventing the driver needing to lean out or jump up to dash across the cab. BUT, I did think this option could pose a potential risk. While shunting, the train radio set is to the yard shunt channel. To remotely operate turnouts and or this level crossing, the radio needing to be altered to the switch channel. Then, within the switch channel scrolling to find the specific switch frequency necessary, and hit enter to activate. Finally, swapping the radio back to the shunt channel. All of this period, the driver would NOT hear any instructions from the rail operator on the ground. YES, train movement being AWAY from that operator would not be as dangerous as when towards the operator. However, I did think it did pose a risk potential. Level crossings can pose dramas and fiscal challenges for railways. Unfortunately, complete grade separation between road and rail is not possible at many locations. Those problems now avoided in Tassie by the closure of the Hobart suburban line, and relocation of the freight yard outside of the suburban region. Steve.
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caniac Regular poster 312 posts
caniac

Steve said: "I doubt that

Steve said: "I doubt that slow speed short lines would possess both track circuits."

Depends on the technology used here in the US. All predictor or motion detector activated crossings -- regardless of railroad class -- have a low frequency approach (< 1kHz) circuit and a high frequency island circuit (4kHz-20kHz). These are the vast majority of crossings in service today. There are still some DC-only stick circuit crossings -- getting rarer all the time-- and also there island only crossings where a train is required to stop and wait for 20 seconds up to 70 seconds or more (depending on if a traffic preemption timer is in use). Circuit is usually AC out/DC back or a low to mid frequency transceiver. A DTMF-controlled crossing can activate a preempt timer, which can then activate the crossing when time expires, or simply activate the crossing for a pre-determined time. But the crossing will always have some means of activation as long as the island is occupied; "positive island ring" required per federal law CFR 234. DTMFs from Larry McGee have an internal recovery timer which is programmed in the field before the unit is cut over.
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