Railfan Technology > Could I just hear ATCS data by ear and get useful info?

1.Could I just listen to ATCS mobile side data bursts and get good local information by the tracks that something is coming and a siding about to be used? (kind of like listening for EOT's) only I would know 2 trains would appear shortly. Let me explain, I plan to move right by a track using CSX ATCS in Tennessee, north of Nashville on Henderson Sub. There is a long siding and switch near there with antenna, like within a block of my home, which will wonderfully adjoin the tracks. My question is if I just listened for the data bursts on the mobile side with a scanner without much of an antenna would I hear the bursts ONLY when the switch is commanded to change state? Or, is there some housekeeping or polling that goes on that would say make it respond every 15 minutes or something, which would make listening that way worthless? I know about the Yahoo ATCS group but they seem to want only questions regarding their program, so I ask here. I want to know more about how it works radio wise, from what I see a train entering/leaving a new block would generate a signal too, but I am in middle of a block. So question is do ATCS devices only radio back when given a command to do work on that 896 Mhz freq band?
2. What is main difference in the new PTC coming from what ATCS is now? Seems awful close. Does it just add GPS and a keyboard to get messages on or something a lot more? I assume ATCS will continue as part of PTC, right?, what else will I see happen when we get PTC?
3. Where do I find out where the BASE stations are for ATCS on a line? Are they normally every so many miles like track detectors are or what?

Simply put, no.

KG

The ATCS example I saw converted the real time activity onto a display of the main track, with sidings and names etc. The display was static until a new command or report became available, which then changed the display in the appropriate manner. After many questions, apparently the information could be logged on a timeline, what most of us know as a log, in simple codes or sent through a data base table to convert into identifiable locations or actions.

Perhaps the log could be scanned or searched for key words, locations or known changes in status. In a similar manner, perhaps the log could be scanned for a known progression of codes relating to a moving train and then a message sent out, or light bulb, whatever.

Most folks like the traditional CTC board display. I wonder if it's worth the extra effort. Or if one is retired it would be an interesting task. The timelog may be as useful for other applications.

But listening to the ATCS traffic as if it's in Morse code. Nope.
Or maybe something similar? Nope.
The modulation and repeater designs remove proximity from the received transmission. My understanding is that each antenna location also act like a repeater to move the info from the remote site to the location hard-wired, or fiber, to the company Network. Ergo all the locations broadcast the new info, that's why a trackside user can determine what's happening at the other end of the district.

There are unique characters for known locations though. It's not in an easily deciphered 'code' though. It's more of an assignment of a unique set of characters to a location or action.

That's how I understand it, maybe there's something else to it. I haven't tried my hand at it, it's too much like the work that I do for a living.



Edited 1 time(s). Last edit at 06/10/11 17:36 by TCnR.

There are some ATCS sound clips here - http://www.atcsmon.com/samples.html

1. No, listening wont really help you much although you will get a few bursts back to back when a train is going through a control point...

2. As far as PTC, it has nothing to do with ATCS. ATCS is a protocol for the codeline between the Dispatcher and wayside control points to set signals, throw swtiches and show occupancy. PTC is a safety overlay to prevent trains from getting too close, going overspeed, etc and subsequently will apply the brakes to stop a train that has become unsafe in a number of ways.

3. Base stations are considered BCP's and are the towers that transmit the commands from the dispatcher to the control point as well as receive the indications and acknowledgements back from the CP. They are typically spaced about 20-30 miles apart depending on RR preference and terrain in the area. The actual control points are considered "mobile" points and are located whereever a dispatcher controlled siding, crossover or even a holdout signal is located.

I would encourage to focus your ATCS questions on the ATCSmon Yahoo group where there is a wealth of resources and knowledge. Keep in mind that not every line on every railroad is ATCS.

Hank
Roanoke, VA ATCS / AUdio Feed Admin



Edited 1 time(s). Last edit at 06/11/11 00:12 by hdralleiii.

1. OK, let me clarify my question a little. Let's say you have a block and there is NO train traffic coming at all and nothing is to be changed track wise. Would the mobile side 896 Mhz frequency be totally silent until someone does want to operate a switch or a train enters the block? I think everyone is reading too much into my original question. Think about just listening for EOT's for instance, you do not decode anything, the presence of the EOT signal itself tells you a train is nearby, see? I wanted to use the same idea to know when a siding is about to be used, which would mean 2 trains are soon to be there and it is time to go to the road bridge over the tracks for some good photos.
2. Speaking of EOT's, is there a program and equipment to use with a PC to decode an EOT signal?

If you listen to the ATCS sound clip referenced above, you will hear a difference in signals dependent on whether the signal is SCS 128, Genisys or something else. The base(BCP) signal is more of a constant stream while the mobile(MCP) signal is more intermittent and, in my experience, does change as a train approaches. I have only heard Genisys RFL which is the Genisys signal on the sound clip.

Good luck.

Mike



Edited 1 time(s). Last edit at 06/11/11 13:07 by PALuvR.

Silverstreak Wrote:
-------------------------------------------------------
> 1. OK, let me clarify my question a little. Let's
> say you have a block and there is NO train traffic
> coming at all and nothing is to be changed track
> wise. Would the mobile side 896 Mhz frequency be
> totally silent until someone does want to operate
> a switch or a train enters the block?

Nope - the system is constantly rechecking that it can communicate with the MCPs and confirming their status. So it'll be noisy all the time.

> 2. Speaking of EOT's, is there a program and
> equipment to use with a PC to decode an EOT
> signal?

I think the ATCSMon group used to have such a thing. Never tried it, but remember seeing it.

If you could, I would suggest applying for a job with the US Navy as a sonarman, or with any of our nation's foreign intelligence services for doing work in the ELINT world. You obviously would be a very talented and therfore valuable individual. :)

-Eric

Thanks NDHolmes, that is what I wanted to know. I still have a feeling this may work for me, just a little differently. Since I would be right by the switch, I would use a scanner with just a tiny antenna, maybe an inch or two wire, so I would ONLY hear that one device on the MCP freq. Now if it does do the status and polling there would be regular short chirps from it as you predict, BUT I bet when it is set there would be a real long data burst or a whole bunch of short ones all at once, which means it would be able to convey to me by sound that it had just been set. Another interesting thing Pal mentions is that the bursts have different sounds and I bet the status ones are all the same but the commanded ones sound totally different. I will start listening on my next trip and I don't think there are any other ACTS devices nearby to it, will find out I guess, it is far from a block edge.



Edited 1 time(s). Last edit at 06/12/11 06:51 by Silverstreak.

Another thing to consider. The dispatcher may line the route way in advance of the next train movement. Sometimes if you know the next move needs the switch reversed, you go ahead and line it reverse when you think about it, even though it might be hours until that train appears. Just the fact that there is code line activity at the control point does not necessarily mean a train is coming. Could also happen when blocking is applied for a track authority. So you might see nothing, or just a hirail truck or tamper. This would of course, be more likely during the day. It was a good idea though!

Well this track has trains about every 30 minutes so I doubt it would be much of a wait. Since ATCS is just on busy routes I doubt there would be much of a wait anywhere for the next train really. Yes work trains or trucks could set it off too, anything that uses the siding, but actually I want pictures of work trains too so that is fine. The idea is to know when the siding will be in use as opposed to just a train coming through. This would be used in conjunction with hearing the hot box detectors which would tell me trains are coming, but I would also know there are going to be two with one waiting, because the siding switch just changed state. Great for going to get pictures.

UPDATE I made a trip to Springfield Tn and had a couple days to listen. Well, seems different than anyone thought. Yes I could hear the base strong so it is transmitted nearby, and I heard the mobile side chirps too. Here seemed to be the pattern, when the switch is NOT set, no chirps. When it is set, then it seems to chirp regularly, maybe like a minute or so between, during the entire time it is set for the siding to be used. Once back normal it is quiet on the mobile side again. So bottom line is I can't just monitor all the time all that noise but can turn it on and if I hear chirps know the switch is set, so I guess it will achieve what I wanted. Now that I know I can hear the busy base side I hope someone comes up with a good modem so I can display that, the ATCS group talks about items no longer made being needed to do this, not much help there.