SIGNALS 101: 10 Levels of Train Signal Understanding

[@foogeeminipix]

The wavelength of a 60Hz signal is 5,000 km so either you have very long track circuits in the USA or extremely sensitive phase detectors or, more likely, power frequency track circuits don't work the way you describe.

[@Hyce777]

You're absolutely correct, I'd had this explained to me before but I must have been conflating two types of track circuits. It appears there are high frequency AC track circuits that exist that operate the way I've described, but the ones we use that are lower in frequency utilize a vane relay that is looking for a certain amount of AC current to operate. Once the current drops off (due to the presence of a train), so does the relay. Learned something new today, thanks for calling me out!

[@mdavid1955]

@@Hyce777 Aren't Pwr. Freq. circuits the basis of grade crossing protection signals too? ?

[@Hyce777]

@@mdavid1955 Depends; sometimes yes, sometimes no. Usually they are an overlay of some sort, be it audio or power frequency so that the approach circuits can be separate from train detection for signaling. But grade crossings are probably their own separate 101 video. lol!

[@aaronbrandenburg2441]

Hey there is a video somewhere here on KZbin where someone I was saying about is it possible to charge a cell phone from that track signaling circuit and I think it's a saved video that where they've got a lot of speaker connected to cross the rails and you can actually hear what type of signals are being send down the rail it's possible these are two separate videos possibly same KZbinr don't know too long ago. Not sure which circumstances they were in and what type of signaling was used for that track circuit either. But you can clearly hear different patterns and in-between you'd hear something entirely different repeating on a regular basis. So just was not just a constant frequency again not sure what circumstances this was being used or how far a great Crossing or anything there was no reference to it and all you could see was the track at that point. In the old olden days or bad old days if you want to call it that? Almost everything was d.c. and frequently battery-operated either rechargeable batteries at in some areas or even long life primary batteries although some metal-air batteries were used and even the ones that just had two plates replaced and the electrolyte changed in some cases. Somewhere similar to what was used things like aids to navigation. Such as buoys and other other applications as well. And even what was referred to as a charge retaining battery which still unfamiliar with but I knew they existed. And even sometimes even in later buoys they would actually be powered by disposable batteries essentially. Think giant lantern battery! And I believe some systems as low as 4.5 Volt or even 6 volts. I know someone that had two strobe heads from a buoy that had been washed to a location the thing was basically kaput but the strobe assemblies have been salvaged. When it was found was barely even able to float anymore and had probably been out of commission for years! I was able to power up one of the strobe heads the other one the Xenon strobe lamp was truly spent electrodes that degraded so much that it wouldn't even flash at all. Also back in the day Way Way Back a some signals as in semaphores were actually powered by CO2. Back in the day it was called carbonic acid gas! Some signals were actually lit by oil candles even. But the interesting thing is there was some electrical equipment associated with that. Essentially a thermostat of course course relying on two different Metals expensing man Contracting. However are not a bimetallic strip like one might think. And there would be a series circuit that if one of the oil candles goes out the circuit would open since the thermostat but cool to the point that the circuit was open. And that would be relayed to either a signal Tower or otherwise to indicate that there was at least one signal aspect somewhere that was out! Even back in the day there a lot of track circuits. Most people think that all the lines beside a line of crack is Telegraph lines however back in the day a a lot of it was track circuits. Performing various functions not just signaling but various other things as well. As a matter of fact there was even a radio system at one time that was won the first since there was always overhead lines near the track essentially you could do short distance radio just having the receiving system on board the train and be able to just pick up the signals not sure of this was Prototype are actually putting into practice but have heard of it. Also there was actually a communication phone system that could use Telegraph ones for telephone purpose. That essentially the extended hooks over the telegraph line to connect it was an important box sort of thing essentially first portable railroad telephone of course this is before the Advent of Radio Systems. And even before really electrical and other things caught on there was a lot of purely mechanical systems that would operate signals and more. And also some generations of pneumatic systems. And if anyone has ever heard of the old Crossing beacons that just blinked at the Crossing and just had that sort of conical base with the Lantern on top. Those were actually at First at least let buy acetylene gas! Also at one time they let railroad cars by Compressed Gas! Lot safer than kerosene lamps

[@PositionLight]

@@Hyce777 I believe the technique you were discussing applied to audio frequency track circuits in the multiple khz range. Utility frequency AC track circuits I believe worked like a simple DC TC, but could support electrification or DC overlays and just needed the AC relay technology to exist.

[@walterrogers359]

In my 44 years as a conductor, I never realized there was THAT MUCH to consider when designing a signal system. Very informative and educational. Will be watching more of your videos .

[@northwestrailfanofficial]

@ walterrogers359 what railroad did you work for?

[@walterrogers359]

@@northwestrailfanofficial CSX and predecessor lines to SCL from 1973-2017.

[@dvone4124]

I can tell you love your work by how hard you have to restrain yourself from going to Level 20 in your 101 series. Thank you for sharing your passion.

[@DanielinLaTuna]

Very informative! Thanks for sharing. I was once on a southbound Amtrak in California (in the mid-seventies) when we slowed and came to a stop. A few minutes later the conductor announced that we would be waiting for an unspecified amount of time - Kansas City had lost track of ALL trains and had broadcast an All-Stop signal to the entire traffic. No train could move until the system was restored and the location of each train was determined. We were grateful for the explanation, and for the protection afforded to us passengers - there would be no collisions that day!

[@FerralVideo]

My face lit up when I saw the 12 minutes of relay logic discussion. I love relay logic!

[@croom1278]

KZbin signaled me to this video

[@frozen_owl1493]

Shut

[@weylinwest9505]

Silence

[@2listening1]

👍

[@RingLordSonic]

Very pun-ny

[@mikestudioz216]

*BA DUM TISS*

[@lwnf360]

I work for a signaling vendor. This video is better than our own introductory training materials.

[@joshuadupay1285]

I am part of a model railway club that runs out of an old 19th century station in northern virginia, and our stations semaphore for train orders still works. We also have a couple of the hoops that they would have used to give train orders to the train crew. Really cool to see that stuff in real life and it helps to really visualize how things worked in the past. We also run operating sessions on time tables and it is so true even on a relatively small scale railroad how easily the time table can get screwed up and the necessity of signals to keep trains from colliding. Really enjoyed the video as always Hyce!

[@Hyce777]

That's awesome!

[@mikesimmons8762]

I''m a retired engineer. Very interesting. So that is some of what helped keep my trains and crews safe all those years. New sub.

[@MultiMightyQuinn]

This is one of the best explanations I have seen, and this is a topic that really interests me. Thank you for taking the time and putting in the effort to make this video. I really appreciate it, and look forward to seeing more from you. Cheers!

[@vaudevillian7]

Brilliant, coming from the UK I always found US signals slightly baffling so this is much appreciated

[@jovetj]

This explains the logic of US/Canadian signaling very well: web.archive.org/web/20160313144451/alkrug.vcn.com/rrfacts/signals/signals.htm Let me know how it works for you. I'm happy to answer questions you have.

[@Armageddon_71]

Level 6 reminds me of a situation in Switzerland. Appearantly they use some method (probably with weight sensors rather than electricity) to count how many axles have passed that point (probably use full to indentify runaway cars). I think you can guess what happened when I say a law was implemented that a train cant have exactly 256 axles.

[@jurgenkriebs9405]

An axel counter does not weigh the train it just use an 8 bit value so you would zero for evry 2^8*n because you do modolu 2^8 to a binary value

[@TrapperAaron]

Uhoh runaway bits!

[@Armageddon_71]

@@TrapperAaron More like "Train? I've seen no train it says 0 axles passed" followed by kaboom.

[@dasy2k1]

It's an axle counter, uses a magnetic field to count wheels. You have one at the beginning and one at the end of the section. It counts +1 for each axle entering, -1 for each exiting 256 axles on the earlier versions made it think the section was clear

[@MmeHyraelle]

Hahaha the byte is full and goes "ah, its 100000000, its clear"

[@DB-thats-me]

Red on the bottom… Yours is the best explanation, in my 38years railway experience for this situation. 👍

[@russellrattys6581]

Im in the uk, my grandad told me semaphore signals were set to high for go, low for stop, because if snow built up on the signal and forced it down, that would be a fail-safe, so trains would stop, and telephone a signalman to check whether they could pass the signal or not My friend went over to America to work on the advanced train protection system, basically if the train ran a red light, power would bw cut from the motor to the traction motors, and the brakes would be applied

[@DB-thats-me]

Correct. In places like Britain, who use lower quadrant semaphore, the arms are counterweighted so that if the control wire breaks (fails) the signal will will ‘fall’ to stop. The safer indication.

[@Two_Bears]

Thank you! So much fun to see this! I started in the Navy doing motor rewind, then progressed in elevator logic’s and computer controlled motor theory. After I got out, I went into software and hardware design until I was designing processor system at board level. Lastly, I went to networking systems. I learned logics long ago so I fell in love with these relay systems you showed here! Unfortunately, now I’m old and just want to stare at choo-choo’s and not think anymore. The most complicated thing I do now is trying to understand my navel.

[@Hyce777]

I totally understand that vibe, haha! Glad you enjoyed.

[@jovetj]

_“The most complicated thing I do now is trying to understand my navel.”_ ROTFL! I salute you, sir.

[@kleetus92]

Guy I used to work with when he was going to school (he's near retirement age now) used to work for Union Switch and Signal here in Pittsburgh PA, and used to wind coils and build the glass case relays. I was always fascinated with those, especially where a few of my local lines are still running them today. You can hear them clicking away when the clear signal is set, then after the train hits the block ahead of this position it goes from (I'm guessing) 120hz click click click to 60hz click and then as the train passes the block and signal it drops from green to yellow over red, and then as it exits that block, it just goes dark. I've spent many an evening watching the lighting bugs and listening to those relays talking waiting for the B&LE to pass by.

[@jovetj]

Signal code relays are very neat. It's how the signals talk to each other, so when a signal is at _Stop_ (no code, no clicking), the signal in front of it knows to show _Approach_ versus something better. It's also what the conventional cab signaling listens to.

[@lordsherifftakari4127]

understanding Track Signals is also handy for Trainspotters and Train enthusiasts to know what is going on in their area when a Signal is nearby. speaking of dispatching, when are you going to take another go at the Dispatch simulator?

[@ianburnett7333]

Track Ciruits are not something that terrorist should know about, If you connect 2 Track Ciruits together with a pair of wires, cross them over, create a false feed, train is not detected, another train will crash into it.

[@lordsherifftakari4127]

@@ianburnett7333 the system is designed with numerous redundancies and fault detectors inside the trackside bungalows and at central Dispatch offices. any anomalous signals detected will send the block signal affected into Failsafe Mode. in Failsafe, the signal will display Red or no Indication at all an error detection will also be sent to Dispatch to send out Track Maintenance to find and repair the fault. Terrorists want to make a statement when they attack. derailing a train doesn't do that since trains derail without manual intervention due to an array of reasons railcars carrying Haz-Mat's are designed to remain intact if involved in a derailment.

[@jovetj]

@@ianburnett7333 "Terrorist" can't do much to a track circuit that mother nature hasn't already.

[@jacebeleren9290]

As an electrician, hearing this track circuit information and how frequency changes alter the expected return phase of current flow hit different for me as I'm currently learning advanced AC theory where the relationships of frequency and phase are important for calculating impedance for AC circuits

[@robloxthomasrandoms573]

Always love the railroads101 videos they are so informational and help a lot for a game I'm making I use these videos a lot to make it accurate to real life thank you! Keep up the great work!

[@TheOneTrueDragonKing]

Agreed.

[@leightonmoreland]

I very rarely feel so literally called out....

[@natecofga4679]

I have really enjoyed these 101 videos on different subjects on the railroad. I was thinking after your 101 on interlocking and junctions, you should do one on the 101 of switches i.e., turnouts. I know the railroad uses different ones to route trains and locomotives. There are the "normal" switches, 3-way switches, double slip switches, single slip switches, and stub switches just to name a few.

[@Hyce777]

Yeah we could probably do a "special trackwork" episode. Maybe that would make sense before interlockings 101... We'll see. Lol

[@snakeyes1952]

This video was very enlightening and showed me more about the signals than I really knew. Thank you Mr. Hyce!

[@dougcook7507]

I live about 20 minutes from Milan where the interlocking tower in the video was located at. This is the first time I have seen that image. Thanks for having it in the video.

[@Hyce777]

Google yielded good results :)

[@marco_grt4460]

I took a hit seeing Michigan Milan (I knew that in the United States you have Rome and Venice, but not Milan), I kept thinking Milan Italy, the bad thing is that google maps for photos of the city also put the Castello Sforzesco and the Vittorio Emanuele II Gallery

[@jeffnordman]

Before I even watch this, THANK YOU!!! As a long-time train enthusiast, you have finally brought closure to so many of my railroading questions! I've watched many of your other videos (still catching up) and the delivery and content are both top notch in my opinion! So yes, as many videos as I've watched "explaining" train signaling, they have yet to "explain" it to me. I'm confident yours will as all of your other videos I've watched have been clearly instructional and explanatory, also with a bit of humor, which is always appreciated! Also, what is a bucket of limes???

[@Hyce777]

The limes are an inside joke on the channel about people making dumb puns or saying dumb things. We jokingly throw them at each other. It's a silly tradition. Glad you enjoy the channel!

[@jeffnordman]

@@Hyce777 That's fun! Thank you for the explanation!

[@michaelschmidt1223]

Your teaching style in these videos makes it so easy to understand. I love all of your 101 vids. Thank you for taking the time to produce them! Keep up the good work!

[@NickCharles]

As someone who's taken some basic courses in computing, this reminds me a lot of the logic gate design of basic microprocessors. I suppose in a way they're all doing the same work, signals are just electromechanical versions of the same, but with a lot more safeguards against undesirable results. Very fascinating stuff, thanks for sharing!

[@dshack4689]

at 9:40 when you said you'll be doing an upcoming 101 on interlocking, I was immediately liked and subscribed instantly, am very much looking forward to that as it is too often an overlooked or glossed-over part of signalling, everyone else focuses on the aspects and semaphores but never much detail nor closeup on the interlocking and interlocking design - can't wait! cheers =)

[@kuhljager2429]

Can't wait for interlocking101 now. This is very well explained, nicely done. Stuff my grandfather has taken years to explain to me condensed into a single video

[@Hyce777]

Cheers Stuart :)

[@jovetj]

With the days of mechanical interlocking mostly forgotten, common railfan knowledge and understanding interlocking principles has sadly, err, fallen by the wayside. But it's just as critical to safety on the rails today as it was 100+ years ago.

[@garysprandel1817]

Very informative Hyce. Yeah having CNW as the hometown road you always knew any run through power was going to be trailing. I'm on Uncle Pete's former CNW Chicago/ Twin Cities Muscle Line ( or northwest line as we locals called it) and was for some odd reason had a different variety of ATS than the rest of the system and it meant that in the days of common power swapping between CNW and UP even dual system ATS locomotives couldn't lead on the NW line. That did work out even into the UP era that meant until UP finally got the PTC up and running last year the few freight trains( sadly in a fit of budgetary cuts in 89/ 90 or so there's a lot more bike path than track between Chicago and TC and GM closing the Janesville WI plant killed nearly all freight traffic on the line)that ran had a SD40-2 pilot locomotive for ATS reasons. I understand the need for PTC but I do miss the ability to discern what railroad you were encountering if you had no map or train to identify the line or at least it's heritage by the type of signal it used.

[@jackglossop4859]

I love that the equivalent in aviation is just a a bloke looking at the runway to make sure there’s no plane on it.

[@rottenroads1982]

As someone who has been taking Railroad Training Courses, I do know about the information. And I learned about 4 different Speed Signals. First is the Yellow over Flashing Green: This is the Approach Clear Sixty Signal. Second is the Yellow over Solid Green: This is Approach Clear Fifty. Than there is the Red over Flashing Green: Diverging Clear Limited Lastly there is Yellow over Lunar: Approach Restricting (with speed of 15mph).

[@unionsims9501]

I always think I know how something works on the railroad. but then we get to level ten and it is like what is even happing right now. I will never look at a Train signal the same ever again. Thx for the great video.

[@steveholloway738]

Watching part 9 reminded me of a conversation I had about CROR (Canadian rail rules) #564 - authority to pass a signal indicating stop. The rule is simple, but seeing how many things have to be checked, I bet it’s a headache for RTC to issue that authority.

[@jovetj]

That is why Call-on signaling has gotten more popular. I don't know of its status in Canada, but CSX uses it all over. It allows the dispatcher to signal a train past what would be a _Stop_ signal into an occupied block with an upgraded _Restricting_ signal. This maintains all the safety features of the interlocking plant while avoiding just talking a train past a _Stop_ signal.

[@steveholloway738]

@@jovetj we do have restricting signals as well - they are actually fairly common - however I’ve seen trains request permission due to signal malfunctions approaching a single track section. There are several ways to indicate restricting speed within the Canadian rules.

[@johnrogers2849]

Honestly had no clue that I wanted to learn so much about steam locomotives and all other train related knowledge. Awesome videos!!

[@ianfoster8908]

Great to see Parkes and Orange track display from New South Wales, Australia. I note that others have referred to axle counters; these are used on the Adelaide suburban network where the aspects are direction based . The earlier system and that in use on the rest of the state of SA (where there are fixed signals) is speed based which is the general case in the USA. The relay logic took me back to my early days as an EE in a steel works where conveyor and process drives were interlocked the same way but with somewhat less verity.

[@michaell.maloney4026]

It’s 11:24 in the morning….I need a beer already…..OMG, what an awesome explanation…just of the relays…..I sincerely hope they pay you really well for the amount of responsibility you have to make sure this works. Loving this whole 101 series. Keep up the good work.

[@neiloflongbeck5705]

Trip stops (or in the UK trip cocks) are still in use on London Underground to stopmtrains passing stopmaspects. They were also used on parts of the North Eastern Railway where it was known as the Raven Fog Signal that caused the whistle to sound if the trip cock was set to repeat a stop aspect.

[@neilcrawford8303]

They're also used on Chiltern line trains where they share the London Underground lines. Also Merseyrail use trip cocks.

[@queens.dee.223]

NYC subway has these as well and I think uses the same terminology.

[@bixfisher]

Absolutely fascinating! I have been interested in railroad signals since I was a child watching trains with my dad. Searchlights fascinated me the most! So well done. I am hooked on your channel.

[@jovetj]

Railroad signals are great. It kinda baffles the mind that a little 8-inch light controls what a million-pound train does.

[@littlegp18]

Searchlight outer roundels are 8 3/8 inches

[@d455ave]

Very interesting. I have designed various smaller non life threatening relay logic things, and state machines using logic gates and flip flops, etc. Including a fancy at the time audio switching system where the operator set various channels on and off by pressing keys. The system sent commands on the audio using nonstandard DTMF signals, the remote ends decoded, set switches, and replied via DTMF so the control box would light indicators that the command was processed. No microprocessors involved in that one.

[@commodoresixfour7478]

Thanks for the refresher on interlocking towers. I used to drive for a living and one time I got to visit Marion Ohio. I like site seeing and discovered their train station. Believe it or not, I randomly walked into a train club meet. Because of this I got to play with their (restored) interlocking tower. It was awesome. They had it setup so you could pretend like you were controlling the double Dimond.

[@kilroy_was_here1]

Thanks for putting the time into this video! I have learned that I would go insane as a signal maintainer and that I should avoid the job at all costs. In all seriousness, thanks for what you do! I’ve learned SO much from these 101 videos. I look forward to the next one!

[@jovetj]

I think I'd really like the job! Except for the heights on those bridges and cantilevers...

[@kmed92]

After working for 15 years as a traffic signal foreman, any time I dealt with RR crossing preemption, I was amazed. Even though I LOVE trains, I turned down a job offer on a signal crew. I regret it to this day. Excellent video man. How have I missed your channel? I'm glad YT pestered me to check you out. Had to sub! 👍

[@Hyce777]

Cheers mate! Preemption is a neat thing. We're going to do a grade crossings 101 sooner or later here and we'll get into that.

[@kmed92]

@@Hyce777Cool. I'll be waiting. 👍

[@neilcrawford8303]

We have 4 aspect signals on some routes, sequence is red, single yellow, double yellow, green. What us odd to my eye is the change over to LEDs. On the roads the LED traffic lights still have individual aspects, separate lens for each colour, while on the railway they've adopted multiple colour single aspect lights, or two aspects if you require a double yellow signal. Thanks for your video, tge US signalling is quite different to the UK in some ways, but looks like it can convey more information through the various aspect combinations.

[@jamesphillips2285]

You are required to have normal colour vision (or at least pass a test that you can distinguish the signals) to conduct a train. This is not required for driving on the road. So the orientation of the signal head distinguishes between the red and green light.

[@velikiradojica]

For use on 25 kV 50 Hz electrified rail lines they also use track circuits that work on 83 and 1/3 Hz, the power being injected on one side of the insulated joint and being recieved by a motor-relay on the other side. It's a pretty old system, and used to use a motor-generator group to produce the odd value sinusoid by using the motor running on 50 Hz. Now it's usually generated by electronics.

[@TheOneTrueDragonKing]

As a side note, for those familiar with Lionel model trains, the track circuit signalling system is VERY similar to track blocks set up to trigger accessories and signals there. The main difference is that the middle rail is "hot", where the power flows into the track circuit, and the outer rails are "ground".

[@akhenaeravaaldryn]

I love the detail you have of all these systems. I've always been fascinated by logic circuits and they tend to come fairly naturally to me. I designed the logic circuits for my own CNC mill, and it was such a fun thing..which is probably not what most people think about complicated systems like this. But I love it. I bet this is a fun job. Thank you for sharing

[@cemmy410]

About two weeks ago I tried to go on a signaling deep dive but didn't find much info, so I'm really looking forward to this one

[@Hyce777]

Good :)

[@jovetj]

It's a complicated topic because of its diversity and the details are just not obvious. But railfanning is fun because there's always something to learn on the railroad!

[@ICUNA22]

2:10 In the early days, trains operated by Train Orders - Track Warrants are a relatively recent form of track authority. Not being nitpicky - they are vastly different!

[@Hyce777]

That's absolutely correct, bad use of terminology by me. Cheers :)

[@jeffhergert4614]

If you want to be very nitpicky, the first method, as described in the video, was time table only. The first telegraphed instructions that developed into train order operation was issued in 1851.

[@northernadventurer160]

As a UK signal engineer you done an amazing job well done!

[@DFX2KX]

there's a railroad mod for minecraft, and that's what got me into trains. it has switches, and addons to that mod have signals too. I've used computercraft before, so tried to program computers to control just the three little sidings I had so that I could hit a button and put my train in that particular place. I never managed to get it all to work properly. it truly IS madness.

[@jovetj]

Actual train simulation software is much more fun than that.

[@DFX2KX]

@@jovetj except driving trains around is quite literally ALL you do in a game like TrainSim/Dreail Valley/RRO. Minecraft lets you use Trains for actual logistics. Wanna move spoil out of a mine, have someone else in another part of the server that needs a crapton of cobble for a build? Trains.

[@DFX2KX]

it's like getting the traffic flow mod for Cities Skylines as opposed to just running ATS/ETS or City Car Driving. It's a tool to meet goals. both are good, but they're very differant.

[@Squant]

@@jovetj Shame all of the major ones are notoriously predatory with their business practises, not to mention poorly optimised with weak post-release support.

[@Ebolson1019]

Where I work we build the physical bungalow boxes and there have their own redundancy. The lid lips over the sides, all welds are water proof, and there are 4 drain holes with the box sloped slightly towards each to keep water out.

[@Dallen9]

I'm just going to leave this little side note for 5:11 , Traffic signals actually were designed after Train signals and the Semaphore displayed in this section of the video is what modern traffic lights mimic. you even see the Green on bottom yellow in the middle and Red on top. As Hyce mentioned Railroads look for the high position of the signal(i.e. the flag on the Semaphore) so when the change from Semaphore to Light signals happened they had to flip the colors upside down so that the older Engineers could adapt to the new electronic signaling faster. Now I'm skipping some funny business that happened during this transition and the reasoning why this happened. I know some people who've long time rail spot might even point out that the current electric signal layout wasn't always that way. just note that's the funny business I'm happily skipping over. This is also apart of the root reason why Signaling diagrams for Rail signals is such a mess.

[@Hyce777]

Cheers Dallen :)

[@Dallen9]

@@Hyce777 Cheers to you too Hyce.

[@cardiffian558]

Hyce: this is an excellent video which covers the essentials of signalling. 'Thank You' from a retired Signal (design) engineer with the former British Railways Board H.Q. The reason that the red aspect is located at the bottom of the signal head array is safety. With incandescent lamps, a curved hood is provided above the lens to prevent sunlight being reflected by the internal mirror giving a false indication. However, during the winter, snow tends to build up on the top of the hoods, which obscures the light from the lens above it. Having the red light at the bottom, with no hood below it, eliminates this risk. Of course, with LED lights, hoods are not necessary. In the UK we use vane relays set at 83.333 Hz for track circuits: this is not a harmonic of the 50 Hz traction supply so they cannot be affected by the return current.

[@Hyce777]

@@cardiffian558 that's a neat piece of additional info I hadn't heard of regarding red on bottom. Cheers - and cool about your vane relays. We use 100 hz for the track circuits I work with, same thing about no harmonics. :)

[@TheTrainWatch]

@@Hyce777 on the other hand, for roadway signals the red ended up on top partially due to the much more variable terrain for cars. The most rolling of hills of trains are still relatively flat for cars and you can see for quite a long distance. But on a road, you could have rolling hills and they wanted to make sure that as you crest a hill, the first signal that could be seen would be red.

[@apollosaturn5]

Excellent video, I love the 101 series. My favorite is the one about air brakes. I knew they worked on air pressure reduction, but, I had no idea about the details. Thanks, man! Can't wait for the next one.👍

[@tomw86]

I am a PLC software engineer. I’d love to have a go at signals design as a job. It sounds so good!

[@Hyce777]

Well the industry is always looking for more folks... I'd say apply!

[@tomw86]

@@Hyce777 I’m U.K. based. Weirdly it’s REALLY difficult to get into here, especially at the level I am at professionally in the rest of my career.

[@scotrailfan170]

It's amazing how different signals in the US than the UK semafours and still used all over the UK and used and are so different of course normal green red orange electric signal but more city area good to know different areas of world

[@buzzytrains9037]

victoria in australia actually used GNR somersault signals and american style 3 position semaphores

[@jacobpfeifertrains1998]

My basic understanding for Union Pacific signals is green means clear for at least 3 bocks, flashing yellow means you have to stop in 2 blocks, yellow means you have to stop in the next block and red means obviously stop. When 2 heads exist the top head is the main and the bottom head is usually a diverging track. If the bottom head is green you can enter at track speed, if its yellow then you must slow for the switch and red means stop or the switch isnt aligned that direction. Thats the limit of my basic Union Pacific signaling understanding.

[@ramoncatano8125]

My grandpa was a signal maintainer then inspector before he go injured on the job which forced retirement happened in 2001, he explained that tracks are mainly grouped in 3s, if the first light is green, go, if its flashing yellow, slow down a bit. Then 2nd light is yellow, it means slow speed, expect next light to be yellow or red. Then 3rd light can be red, yellow or white which means slow down as much as possible

[@TheRealPauseacorn]

Your 101 videos are really helpful. Next week I have an interview for being a Conductor Trainee for BNSF in Colorado, and hhoping that being somewhat knowledgeable of all this will help me out and give me a better chance at it

[@railwayjade]

Thanks for the explanation, on the railway where I was a driver, outside the Depot Yard we had those harmonic track circuits and I wondered how they worked! Besides the silver box pairs, the side of the rail is also stenciled with TX and RX (I assume this means Transmit and Receive) and then a serial number. As a driver we know about track circuits but not exactly how they work so this helped me understand a lot - thanks! I do wonder though why in the depot we utilise the track circuits with the gaps in the rail as opposed to the mainline with continuous welded track.

[@Hyce777]

cheers mate - yes, TX and RX are transmit and receives. If you have signals around the depot, you have to use the gapped type if the signals are the method of enforcement. The gapless / audio style circuits have what's called "pre-shunt" and "post shunt" where you will actually show up early, sometimes within as much as 30-50 feet depending on the circuit setup. That means that the signal will change that early, which can easily cause confusion, so signals are almost always co-located with insulated joints. If you don't have signals - couldn't tell ya. haha

[@IamTheHolypumpkin]

There's a great video from Tom Scott where he shows how German Railway Inc. better known as "Deutsche Bahn" or just DB is training dispatchers using a model-railway. They wired old interlocking levers, mechanical electrical, relais and modern computer system to a model railway.

[@Hyce777]

Yeah, that video came out and I about did a spit take. lol. It's awesome.

[@aaronbrandenburg2441]

Yep I saw that one great video

[@neiloflongbeck5705]

You can still see the Lancashire and Yorkshire signalman training layout in use at the NRM in York.

[@trainman2615]

Honestly, I was a little disappointed by his video. I was trained on one of those systems and there were just too many inaccuracies, probably quite a bit got lost in translation. Fortunately, for as far as I can tell, this video here is spot on in just about every aspect.

[@bordershader]

@@trainman2615 every aspect? Groooan

[@nigelparks6855]

Loving your work - British rail enthusiast here 😁

[@aircooledhead]

OMG! This is SO nerdy! IDK why KZbin suggested this, and I didn’t intend to watch it. But I found it so intriguing, I couldn’t stop.😊 Information I never thought about, dreamed of knowing, or will remember much of, but enjoyed it greatly.

[@GodschildinNC]

Thank you for the info. I am finding it really interesting. I had no idea of how complicated it is. High ball and keep on!

[@Mcdctom]

Its so interesting to hear the electro-mechanical releys in signal bungalow. Fun to hear the flashing yellow light generated by the responding relay. A lot of them still in operation around here.

[@Hyce777]

Yeah, they have a really satisfying "clunk" to them, don't they?

[@Mcdctom]

@@Hyce777 True. And they are not producing wierd issues. There was a unique problem one of a level crossing. A 2 lane main line had the responding "attack" points for red signal. If 2 train entered 200ms difference to the sensors the singals wont change to red. So trains could pass through about 130km/h max speed to an unsecure crossing. The problem was caused by the fiber optics latency. Sadly there were some recorded instances when this happened but no accident happened.

[@jovetj]

The code relays are what I enjoy(ed). You could tell the signal indication just by the rate of the sound.

[@whoever6458]

This was really cool and some excellent electrical engineering! I think this explains why there was a crossing that went down for several minutes but no train ever came through and then when I later saw workers doing something inside the bungalow. What I do wonder is whether it also explains this weird, thick piece of glass that I found when I was walking on this public walking trail that runs next to the tracks (but at a pretty safe distance). I saw the glass glinting in the sun a bit nearer to the track and I am curious by nature so I had to go see what it was. It was broken, green glass with what looked like threads of a screw on the inside of it. It was too interesting not to pick up so I picked it up. When I sat down to have lunch during my hike, I took a picture of it with my phone and did a photo search to see if I could find out what it was from. It turns out it was an old glass insulator that the internet said could be used on high voltage lines and was sometimes also used on train tracks. Although the high voltage lines aren't very close to where I found it, I assumed it still must have been from them because I didn't think there was electricity on the train track and it wasn't near any of the bungalows but maybe it had been a part of one of those insulators between track sections. Perhaps that's why both the local crossings had come down at odd times and why there were people working on the bungalows shortly after all of this. In any case, the glass was really cool and it's too bad the one I found was shattered to bits.

[@libra3655]

So I actually understood a good deal of that based off of other stuff I've tangled in... at the cable company we deal in higher frequency signals in the mhz range, in my area the plant runs between 5-700 mhz. Prior to the cable company I did satellite where they controlled where the dish got its programming from, which ran off of 13v and 18v currents and more advanced dish systems also had a 13v and 18v pairing with a 22 kHz tone. When the signal was split off of the dish for multiple tvs it ran through a multi-switch, which would have assigned where it got its programming from based off of what the box requested and where it would find it.

[@NicoDaycon]

Very fascinating. Creating signal systems is my favorite part of route building in any train simulator. Just another reason why I regret not studying engineering...

[@jovetj]

That's also why I got into train simulators back in the day.

[@bordershader]

My partner's a signals expert for Dovetail Games' Train Sim World (who do US, UK and German routes in the main), in his free time he studies routes literally all over the world (currently has South African, New Zealish, Spanish and Brazilian routes under the microscope) - so I have a second-hand appreciation for the sheer wealth of practices around the world. Clever stuff! Me I'm into motorbikes so much of it goes right over my head, so I really found this vid super helpful. Never knew that about high ball >adopts it into lexicon< Thanks! BTW 41:49 "Ting! our choo-choo can go" 😄

[@jovetj]

Dovetail can't have enough signals "experts" for sure.

[@bordershader]

@@jovetj he's ex-S&T for a preserved railway - the only one in DTG with an actual rail background instead of gaming.

[@bordershader]

@@jovetj so I showed your comment to my partner and he got super excited and said that DTG uses your charts, and thank you for them.

[@jovetj]

@@bordershader 👍

[@21Trainman]

Nice video, you just brought me up from a level 3 with your excellent explanations and clear delivery. Kudos! If you find complex relay circuits interesting, I might suggest Technology Connections’ videos on his electromechanical jukebox, it’s some really cool stuff.

[@rossmcconchie1316]

One of the most important differences between rail and road signalling systems is that there is a SIGNIFICANT difference of the reaction/response/physics between a train and a road vehicle. Train signalling systems therefore have to provide or be decided by forewarning/conditions ahead, not just on-the-spot go/stop.

[@worldtraveler930]

Soooooooo, little silver box near intersection "Equals Bullitt Magnet!!!" 😁

[@TheStiepen]

As someone who has invested quite some time (as a hobby) diving into German train safety systems (signals, dispatching systems, etc), this is pretty fascinating. Obviously a lot of things have overlap, but there are actually some interesting differences.

[@PapaBear6t8]

As a newbie in Train Sim World (that's why I watch this video), I find the German system more user friendly than the American counterpart... not to mention that the Americans don't have a standardized system for the whole country. Each railroad company has their own set of rules and I find that quite confusing.

[@TheStiepen]

@@PapaBear6t8 careful: Germany has 3 major signal systems, depending on time and location. And especially the Hl system (all signals built between I believe 1950 and 1990 in the former GDR) is really confusing and complex - it has 17 aspects iirc. I'm not sure any routes with that system are included in train Sim world though. The Hv system (the one where the distant signals have diagonal lights) is reasonably easy to understand and the Ks signal (the one where you only ever see a single active light on a signal) is the most modern system and imo easiest to understand.

[@PapaBear6t8]

@@TheStiepen Thanks for the info!

[@Ztbmrc1]

I like your way of explaining by these drawings. Here in the Netherlands we have inherited the rail technic from the US, including similar signals and level crossings. We use that dc track circuit, also on lines with 1800 v dc overhead power lines. There is only one thing: the train shortens the circuit resulting in the relay to fall of: track occupied. But at the same time the train also short cuts the battery. Now that is not possible. You can not shortcut a battery. So how do they prevent the battery from being shortcut? On top of the track circuit we also have the automatic train control system (also US origine). It sends 75 Hz ac through the rails, and the rate that it is switched on and of is the code for the max allowed speed. This signal is picked up by two coils on the front bogey of the train, one on each side. A on board system generates a speed indication on a display in the train cab. So we have 3 signals going through the track simultaneously: return DC 1800 v train driving current, some voltage (what?) dc track circuit train detect current, and the 75 Hz atc signal. So that gets complicated :)

[@Hyce777]

That does get complicated! A lot of our systems also use the cab signal with loop pickup as well. My transit system does. It's neat.

[@charlescrawford7039]

Thanks for this great vid. The Pennsylvania Railroad had a series of unique disk position light signals. Some of these are still in usage on the Northeast Corridor between Washington DC and New York.

[@jovetj]

The Pennsylvania Railroad invented the _Position-Light_ signal. The idea was to use lights to mimic the arm positions of a semaphore. Originally they started with four lights in a row, but switched to the 3rd generation 3-light versions once they were found to be perfectly satisfactory. All of the lights on an original PL signal are a fog-penetrating yellow. At some point, after some kind of accident, some moron decided that Red for stop would be better, so the --- lights were changed to Red (which is actually much dimmer!). Modern position-light signals on the Amtrak Northeast Corridor are properly called _Position-Color-Light_ signals, since they have been completely colorized. The Norfolk & Western Railway also adopted position-light signals and colorized them themselves (including the dwarfs!).

[@Shipwright1918]

Personally a fan of semaphores and the manual interlocking towers. The British system of using bell codes and the token instruments is fascinating, have a few simulators of them and it's a challenge to pull all the levers in the right order to keep the trains on time and going to the right places. Love the old oil signal lanterns too, collect 'em and use them all the time.

[@jovetj]

Sure is one nice thing about semaphores: as a railfan, you can read them from the back, too.

[@kenmunozatmmrrailroad6853]

Dear god I learn(ed) so much here… ‘thousand thumbs up and keep ‘em coming!

[@TheOneTrueDragonKing]

Hyce, this is the one thing I wish they'd implement in Derail Valley. Signals that would let you know with a light or position cue when to slow down. This wil be an essential thing once AI traffic gets in the game, but I wish they had them now. Also as a side note you should probably change your preview picture since you're no longer in Railroads Online.

[@jurgenkriebs9405]

I think they did that they use something similar to the german signaling signaling where green yellow means slow otherwise you need a "extra" signal zs 3 or a row of lights cant remember how that is called.

[@TheOneTrueDragonKing]

@@jurgenkriebs9405 Haven't seen that in the game. It needs to be in there though.

[@SchrottiJr]

Big stations in Germany use Hall-Effect sensors for detecting train positioning. Depending on your coverage you can line up trains in one siding with accuracy to a car´s length or less if you chose to. Add hydraulic switches and you can dutch drop 30 cars on to 30 different sidings in intervals of a couple of seconds.

[@teknikal_domain]

It's interesting, watching your videos again now that I work with the rail industry (cab driver for CSX/NS yards around here)...

[@BobDiaz123]

When I worked with embedded systems (single processsor control) we had a Watchdog Timer that had to be Reset at regular times. If the program froze up or went crazy, the Watchdog timer would Time out and force a Reset of the system. At boot-up a check was always done to look for a Watchdog timer Reset and display an error condition. I assume the computers for signaling must have the same protection.

[@stradplayer90]

thank you for taking the time for this.

[@AugustusTitus]

Good video. You cover a lot of ground in a more accessible way than one can expect from an electronics background.

[@pnwRC.]

AWESOME video! I've watched a number of your very informative videos, & decided I needed to subscribe!

[@tomcook5813]

The hardest thing for me to remember when driving in a rail yard, a red light at each track is go for me and stop for the train. I drove truck for ten years and spent a lot of time in BNSF and UP yards. Was always swiveling my head.

[@fixitdude74]

Danny from Distant Signal gives a good entry level understanding of railroad signals and lights, very informative.

[@Hyce777]

And his voice is fantastic to listen to. Yes, I'd recommend folks watch his stuff :)

[@greatsmokymtnsrailfan]

I love how there's a traffic light at the start.

[@Idaho-Cowboy]

So the real question is why are traffic lights upside-down, surely railroad signals came first.

[@greatsmokymtnsrailfan]

@@Idaho-Cowboy hmmmmmm

[@Hyce777]

Dallen9 said elsewhere that they mirrored the semaphores, which have the lights that way, but because engineers look for the physical high position when the RR went full color light they put the green up high... Lol!

[@greatsmokymtnsrailfan]

@@Hyce777 Lamo

[@sterlingodeaghaidh5086]

When divising the signal system for the railroad game I dev for, we created our own system. Being a free drive we had them act more like traffic signals in that their automated, Red = Stop, Green = Go, but where we chose different is instead of having yellow mean an approach or something we used it to signify when there is a danger on the tracks in the form of a line blockage. This is because we still want them to proceed to keep traffic moving, but at a slow speed so they can react to issues that can then be sorted out either by the player or by the admins as we do game maintenance in sessions.

[@Hyce777]

That's a neat mechanic! What game?

[@Silligoose501]

Absolutely fascinating, informative video!! Great job! I'm so glad the KZbin algorithms sent me to you. Such a wonderful person. All the best.

[@TheBeeMan1994]

So I saw some comments regarding grade crossings, and we have multiple types on our railroad, some are simple DC crossings, and some have full preemption. I think the ones with preemption are really neat. And If someone sees this comment wondering how grade crossings work and detect trains, I can explain how one type works. So our crossings with preemption work identical to the one at 21:58, the audio frequency track circuit. Using the same method you describe, with the difference though is that the receiver is tuned to the length of the detected circuit, to the frequency the computer is outputting, the signal maintainer shunts the end of the circuit, and puts the distance into the computer. He does this 4 times on either side, at the full length, 75%, 50%, 25% and 0%, the computer then knows where at each distance the return waveform will be at, and how "loud" the return waveform is, as you go out further, the amplification of the returned signal is diminished, and the computer can use both the frequency and amplification to measure train speed and distance. So this method does a few neat things, one of them is since the computer knows what the amplification is at, based on its location from the island, it can detect the trains distance from the signal, (Like when a train is approaching, the horn is quieter, than when its next to you, then, it listens to the frequency modulation to detect speed, using the Doppler Effect. Think of this as when you hear a fast moving train, the pitch of the horn sounds higher as its approaching, then once it passes, it drops lower, the same thing happens with the waveform as the axle rolls across the rail, the higher the speed, the higher the incoming frequency will be. It can then calculates the train speed based on the return frequency, and the train distance based on the amplification, and then can determine how long of a preemption time to give the signals before activation, Ours will calculate the speed, then based on that speed, it will make sure the crossing lights and bell activate 30 seconds before the train enters the island, and then 15 seconds later, the gates will be fully dropped. If the frequency change stops, and the amplitude stays the same, it will wait, and see if the signal changes again, if not, it silences the crossing and turns the lights off, until it detects a shift in amplitude and frequency again.

[@wictl]

I have always found railroad signaling interesting since I was little and built some really simple systems for my Marx trains as kid. This did lead me into engineering. Thanks for the video.

[@DocEntertainmentProd]

Loved every second of this. Nice work!

[@georgeetherege8347]

Yep -- for more than a hundred years they did everything with relays. The beautiful GG-1 electric locomotives were introduced I 1934 and the last ones retired around 1980 (?). Capable of over 100 mph and utterly reliable, they had not one single microprocessor (!).

[@MmeHyraelle]

I watched a video on train signals before and forgot all of it so lets learn again haha. Thanks :)

[@dasy2k1]

I'm a signal design engineer too, but in the UK where our principles are somewhat different!

[@Hyce777]

It's neat how different the systems are, isn't it?

[@dasy2k1]

@@Hyce777 absolutely, ours dosn't normally attempt to control the speed of the trains but does tell them where they are going... On extremely large speed reductions for turnouts we hold the junction signal at red until the train is timed to be at a suitably slow speed then release it In other situations we have flashing yellows that tell the driver they are diverging but it's up to them to know the route to know exactly what speed they need to get down to

[@jovetj]

@@dasy2k1 We do have some approach-release signals here in the States too, namely on subway signaling systems.

[@ebnertra0004]

I've made a lot of signal systems for a simulator (Open Rails, to be precise), and a lot of similar checks to what the relays do go into the signal script files to make sure the signals show the right thing. A huge plus of that system is that I don't have to descend into the depths of Relay Logic Hell the way real-Worlders do, since it's just assumed the stuff will work without confirming and the 'track circuits' are just assumed to be the distance between two signals

[@jovetj]

Hey there! I "know" you, Travis! :D

[@ebnertra0004]

@@jovetj Uh-oh...you've found me. Haven't heard from you in a while. How goes it?

[@jovetj]

@@ebnertra0004 Oh, just living the dream! You?

[@ebnertra0004]

@@jovetj About the same here

[@jovetj]

@@ebnertra0004 That's good to hear! ;-)

[@CMDRSweeper]

When Norway had... Okay still has, a lot of signal issues around the rail lines of the capitol of Oslo. The one thing we heard "Oh there are problems with the relays" and that was all we got out the media and everyone was like "What is the relay problem, swap the faulty one and make the trains run!" Turns out it wasn't just a faulty relay... Just a really really really really messy relay puzzle that had gotten old and worn out and wasn't that easy to replace :D

[@Hyce777]

sounds about right, lol.

[@CMDRSweeper]

@@Hyce777 To make your signal engineer brain explode, the rail network around the capitol is very much as switchy as that british rail yard you commented on in your train simulator video you did not too long ago :D And with the relays for controlling something like that, the puzzle gets really nasty.

[@Idaho-Cowboy]

Thanks Hyce! This was very informative. It's amazing how much innovation has gone into modern railroading. If you ever want good stories about railroading back in the telegraph days I highly recommend The Boomer by Harry Bedwell, it's an awesome book.

[@ngalasimonmukola3121]

As a driver I only knew to read and interpret the light signals bt had no clue of what happens bt thanks to you now I know but what about the approaching signal ,a double yellow lights for siding track and also cab signals

[@robertbrock2355]

Excellent and answered many questions I had. Many thanks.

[@Naro_Rivers]

When you started getting into relays and mentioned just how complex it gets, my brain just started playing “in the Hall of the Mountain King”.