Railfan Technology > Any luck with PTC data?

With ATCS now becoming non-functional in many area as PTC becomes more universal, I wonder if anybody out there is working on a effort to decode PTC data captured on a scanner.  I have done a bit of work in this area but mine is solely based on audio captures rather than data captures.

ron in far northern California

I don't believe anybody is working on this and if they are they won't publicly admit it.  The data transmission is encypted and breaking that enyption is believe to be illegal.  That would be federal prison illegal.  Also, unlike ATCS where the architecture is well-known due to be publicly published, the PTC system architecture is kept restricted for security purposes.  I HIGHLY doubt that even if someone finds a way to do with PTC what was done with ATCS, that they will be willing to share that knowledge publicly.  The days of monitoring train movements may be coming to a close soon.

As there are competitor companies that supply PTC equipment, it would be reasonable to conclude that the 'details' of what gets transmitted, the format and sequence of data (date, time, location, variable data, for example) would be proprietary to each company and subject to non-disclosure rules and employee agreements.  In all likelihood, the data is also encrypted as well.

Considering that a passing train is continuously transmitting and receiving data and that lineside devices transmit only when an 'event' occurs, the volume of data being transmitted must be considerably more than ATCS transmits and would likely require more laptop computer 'horsepower' to interpret than is currently available.

I have to wonder what PTC activity 'knowledge' would be expected to provide?  That switch #2 at MP 123.41 just moved to reversed position might provide some insight in non-ATCS territory.  ATCS would, of course, show that change.  But of what use would knowing that the crossing gates at highway 123 crossing are functioning normally when the oncoming train is within sight?  I'm thinking it would quickly become 'information overload' with extraneous information for railfan purposes.  I would also expect that the text-only interpretation of each transmission would appear as a very fast moving scrolling of data so fast it couldn't be read. 



Edited 1 time(s). Last edit at 01/26/22 18:17 by BRAtkinson.

"...'information overload' with extraneous information for railfan purposes..."

Too much info for (some) railfans?  Not possible!  Have you never heard of rivet counters?

Is there a published overview of some sort showing the PTC functions? All I hear is about it breaking, curous what it's suppose to be doing.
tia.

TCnR Wrote:
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> Is there a published overview of some sort showing
> the PTC functions? All I hear is about it
> breaking, curous what it's suppose to be doing.
> tia.

The government requirements document is here...

https://www.govinfo.gov/app/details/CFR-2010-title49-vol4/CFR-2010-title49-vol4-sec236-1005/summary


Here is a different view of the system, by a company that wants to sell you test equipment.  Anritsu is a very respected maker of test equipment for the telecommunications industry.

https://www.anritsu.com/en-us/test-measurement/technologies/positive-train-control


And there is always Wikipedia

https://en.wikipedia.org/wiki/Positive_train_control

 

Just knowing the frequency might provide some info that a train is close even if it is just a squirt noise. Any ideas on haw far they transmit the signal or Frequency.

Posted from iPhone

Roger Kujawa
Morton, IL

RogerKujawa Wrote:
-------------------------------------------------------
> Just knowing the frequency might provide some info
> that a train is close even if it is just a squirt
> noise. Any ideas on haw far they transmit the
> signal or Frequency.
>
> Posted from iPhone

PTC operates in the 222 megaHertz frequency range.  The actual frequencies are openly published. A handheld scanner can pick up the data signals.  The transmissions are low power but can be heard trackside.  There are audio variations of the signal coming from trackside which provide a hint of oncoming train activity.  It is nothing like ATCS, however. 

This DOT document provides a bit of background.  It is public. A Google search should bring it up.  The gist of this paper is that PTC relies heavily on encryption as mentioned in other posts.

dot_49646_DS1.pdf


 

The channels are in the 217-221 MHz range. Amateur radio has 222-225. Well, in theory hams can use some channels 219-220 with limitations but I don't know any that do. 

ctillnc Wrote:
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> The channels are in the 217-221 MHz range. Amateur
> radio has 222-225. Well, in theory hams can use
> some channels 219-220 with limitations but I don't
> know any that do. 

I have the following frequency programmed:  220.1275, which worked for me in far nothern California on a handheld. 

This is listed as base #1.   There are nineteen (19) pairs of PTC channels.  If you subscribe to RadioReferene.com, here is a link:   https://www.radioreference.com/apps/db/?aid=7747

The range of those 19 pairs are from 220.1075 to 221.7975 mHz

A PTC decoding effort was posted for a while on several channels on Youtube by a gent who was very software savvy.  He was doing it and showing the program he was developing to do it.
I was following it with great interest.
Then it was blocked and lately I can't seem to find it.
But obviously there are people out there who know how.