EOT devices-how is the signal decoded?

[Aa3rt]

I got to thinking about this today when a northbound CSX empty passed by my location-I keep the EOT frequency plugged in my scanner as trains in this area are sometimes dispatched via cell phone and the only indication I have that a train is near is the data burst from the EOT device. Since I live along a branchline, where we only see loads headed south to the Morgantown (MD) power plant, and empties headed north, there's usually only one train in the vicinity at any one time.

I guess what I'm trying to ask (pardon the excess verbiage) is since CSX's EOT devices all operate on the same frequency, how are EOT signals from a specific device decoded? What happens in a yard, or on a mainline where there may be two or more EOT devices in close proximity transmitting on the same frequency? How does the train crew know they're receiving data from their train and not the signal from another EOT device?

For a look at the railroad operations in my little corner of the world, check out...

http://www.traingod.railfan.net

[fglk]

[clearblock]

Each EOT device has a unique serial number which is included in the transmitted data. That number is entered on the dial on the locomotive EOT receiver when the EOT is placed on the train. In the case of a 2-way EOT, there is also an "arming" procedure when the EOT is set up to insure two way communication and control is established.

Since each EOT transmits only brief data "bursts" ( like packet radio) several can operate on the same frequency in the same general area with no problem.

[oldrails]

I'm noticing up here they seem to be switching over to a two way system. Quite often you hear one databurst then immeidate another one. The back end transmitting a packet to the front end and the front end sending back and ack packet. I'm also noticing that in some cases I'm hearing the EOTs quite a bit further. In reality I am hearing the signal from the front of the train which may be a mile or so closer to me and at the same time transmitting from an antenna that is higher than the Fred on the back of the train.

[b&p rupture]

since CSX's EOT devices all operate on the same frequency, how are EOT signals from a specific device decoded?

Care to share that freq?

[Aa3rt]

Try 457.9375. At least that's what I'm hearing in southern Maryland, this is supposed to be the universal CSX EOT frequency.

[b&p rupture]

Aa3rt :

Thanks for the reply.

[clearblock]

457.9375 is the AAR standard EOT frequency so it is pretty much universal. The HTD (Head end Telemetry Device) frequency for a 2 way system is 452.9375.

The HTD can be heard at a much greater distance than the EOT since the HTD antenna is on top of the locomotive and the EOT antenna is on the box hanging on the rear coupler.

[Engineer Spike]

NS markers and locos have dual band equipment. everyone else was using the AAR, but NS had its own system. Since the Conrail merger, the markers and head end equipment have been modified.

[Pj]

Most if not all EOT systems are two way. That's the whole reason for having that emergency button on the controller

NS still has quite a bit of VHF only transmitters and recievers, but as stated above, they are converting as needed. The frequenices above are nationwide, and NS's is 161.115.

If you have access to ATCS Mon software, there is a second program which will allow EOT monitoring. You will need to modify your scanner for raw audio to the computer in order to properly decode it. You don't get anything too special, other than BP pressure, etc.

[ironken]

I was just surfing when I seen this thread on E.O.T. frequencies. I think you guys interest in the RR is cool and all, but, it is kinda scary how detailed in the frequencies you all are getting. Who cares what frequencies we run on the "D". I don't feel that these frequencies should be displayed on the net. People with a little radio savvy and nefarious intentions could really cause some havoc for us or worse. Just my thoughts.

[Pj]

I know where you are coming from, however EOT, ATCS and related freq's are nothing that the railroads are concerned with. The reason being, 3rd persons (unless they own a EOT controller--and even then) cannot do anything with it. In other words, they won't be able to throw your train into emergency.

The freqencies themselves are also assigned and listed on the FCC website, which is public information by law.

99.9% of railbuff's who use these are using it to gauage when a train is near based on how strong the signal is. There is a software package called ATCS Mon will will allow the decoding of signal/block information and display it on a map that you have to create that will graphically show you what blocks are lined up. That too runs off of licensed publically available information. Due to have ATCS is implemeted, you don't have to worry about someone transmitting information that will throw a red in front of you.

An example of ATCS in action would be the Deshler OH area.

I am all about security and the such when it comes to radio systems...as that's my full time job. If you would like a little more info etc, send me a PM.

[ironken]

Thanks for the info. Now I don't have to worry about the Al Quadas shootin the pill on my train. That is unless they thieve a HED.

[Aa3rt]

ironken-many of us who frequent this forum are both scanner monitors and amateur radio operators. Our main reaon for monitoring railroad frequencies is simply to know when a line may be active. ("Is there a train nearby, or do I have time to hit the 7-11 for a soda and a couple more rolls of film?")

Living in the suburbs of Washington, DC there are many activities that I monitor in addition to my local CSX line. These include local police, town utility frequencies and a couple of local military bases. All of these frequencies are readily available from magazines like "Popular Communications" and "Monitoring Times", available on almost any newsstand or bookstore. Additionally, frequencies are allocated by the FCC and as such are a matter of public record. They can be found on many websites aimed at the listening public. Just try typing "railroad radio" or "railroad frequencies" in your web browser and see how many hits you'll get.

I assure you that the vast majority of us are simply trying to enhance our train watching activities. Having a scanner at trackside allows us to know if a train is approaching or is the line shut down due to a derailment or locomotive failure. Scanning helps avoid those wasted hours sitting trackside waiting for a train that won't show up due to distant problems.

[clearblock]

Thanks for the info. Now I don't have to worry about the Al Quadas shootin the pill on my train. That is unless they thieve a HED.

A stolen HED would not be much of a threat. This is the reason for the arming procedure that requires someone to push the test button on the EOT and then "ARM NOW" on the HTD. The EOT then only responds to commands from the specific HED that armed it.

If anyone tampers with your EOT to re-arm it to work with a different HED, you would get "DISARMD" or "NOCOM" warnings on your HED.