How do trains communicate?

[poltergeisty]

Do they use a series of repeaters or what. I can't imagine that the radio signal from the train could travel say, all the way to Denver from Fort Collins. Do those steal structures near railroad crossings have repeaters in them? Do they use a dedicated phone line or something?

Thanks.

 

[jackj]

I've been away from the RR's for a few years now but they used to use simplex VHF at around 160 MHz. The route was broken up into blocks of varying length and each block would have a VHF base using directional antennas. The antennas were directional along the rail line and the base was connected by the RR's communication systems to the dispatch point which might be several states away. The maximum distance the engine radio would have to transmit was around 15 miles, most blocks were less.

 

[cifn2]

Jack is right, the dispatch has the ability to "call up" a tower in the vacinity of a train and attempt communications. There are no repeaters typically, but some RR's have been reported to have repeaters in certain areas. Communications are simplex also as stated. When a train needs to speak to a dispatcher, they can punch in a DTMF code on the radio keypad for the subdivision they are on, and the closest tower will receive the code, and send back a receive tone, some railroads have a waiting tone, that will beep every so often while they call is pending signalling the crew that the call was received by the tower, and the dispatcher is not available to take the call. The dispatcher then will come on that tower and start speaking to the crew and assisting them.

 

[stevelton]

In the United States, Railroads use Simplex frequencies in the 160-161mHz range.
There are radio towers spaced along the right of way. Some railroads use the same AAR Channel across their whole division, and some railroads have different channels for each main track.

Dispatchers are located at centralized offices. These offices usually dispatch for several different main lines, or in the case of Union Pacific or Burlington Northern, their centers dispatch for most of the country.

They are able to talk to the trains that are in their district by using a touch screen computer to select which tower/towers they want to talk/listen on.

When listening to railroads, sometimes you might hear DTMF tones, this is the train "toning up" their dispatch. The nearest tower then makes the corresponding button on the touch screen to blink, and the dispatcher then knows which tower to select and talk on, saying something like" UP Omaha Dispatcher answering Benton tower, over"
Then the train and dispatcher talk.

There are no repeaters being used by the train crews. this way they leave their radios on 1 channel, and they dont have to keep changing as they move along the track. When they stop to switch cars, the conductor uses his hand held radio to talk to the locomotive (usually less than a mile, easy for a 5w HT)

Steven

 

[cifn2]

In the United States, Railroads use Simplex frequencies in the 160-161mHz range.
There are radio towers spaced along the right of way. Some railroads use the same AAR Channel across their whole division, and some railroads have different channels for each main track.

Dispatchers are located at centralized offices. These offices usually dispatch for several different main lines, or in the case of Union Pacific or Burlington Northern, their centers dispatch for most of the country.

They are able to talk to the trains that are in their district by using a touch screen computer to select which tower/towers they want to talk/listen on.

When listening to railroads, sometimes you might hear DTMF tones, this is the train "toning up" their dispatch. The nearest tower then makes the corresponding button on the touch screen to blink, and the dispatcher then knows which tower to select and talk on, saying something like" UP Omaha Dispatcher answering Benton tower, over"
Then the train and dispatcher talk.

There are no repeaters being used by the train crews. this way they leave their radios on 1 channel, and they dont have to keep changing as they move along the track. When they stop to switch cars, the conductor uses his hand held radio to talk to the locomotive (usually less than a mile, easy for a 5w HT)

Steven

It should be noted that repeaters are not used except in a few yards, which was reported here on the RR forums previously by a user asking about railroad communications.

 

[poltergeisty]

Thanks for all the responses!

So I'm guessing hat each tower is then wired to the phone system to talk to the base station? Because that signal from the tower has to travel an awfully long ways. I know for the airline industry they use fiber optics.

The antennas were directional along the rail line and the base was connected by the RR's communication systems to the dispatch point which might be several states away.

 

[WA1ATA]

So I'm guessing hat each tower is then wired to the phone system to talk to the base station? Because that signal from the tower has to travel an awfully long ways. I know for the airline industry they use fiber optics.

Railroads used to have wires strung along the right of way for communication (all the way back to telegraphs on the 1st transcontinental railroad). Then they went to microwave. Now they are mostly fiber optic for the long hauls.

If you look far back into the history of Sprint, you will find that one of the original companies was the inhouse communications system of Southern Pacific. The trackside microwave links had lots of excess capacity which they started selling off as private line service to large corporations. Then they upgraded to fiber optics. "Sprint"; is an acronym for Southern Pacific Railroad Intelligent Network of Telecommunications.

The continuous, unbroken right-of-way of the railroads is a valuable asset.

One last extraneous trivia .... in the UK, the canal networks have the same sort of advantage of a continous right of way and lots of fiber optics links are either in the canal footpaths or in the canals themselves.

 

[jackj]

Sprint's original name was "Southern Pacific Communications, Inc" and was owned by Southern Pacific RR. Sprint was the name of their long distance telecommunications service. When GTE bought them, they changed the company name to GTE Sprint and later to just Sprint. Almost all of the larger railroads sold excess telephone capacity on their microwave systems as a long distance service. I worked for a company in the '70's who subscribed to the long distance service sold by Pennsylvania Railroad. These services were a pain in the butt to use, you had to dial somewhere around 26 numbers to use them.

 

[jackj]

Phone lines

Thanks for all the responses!

So I'm guessing hat each tower is then wired to the phone system to talk to the base station? Because that signal from the tower has to travel an awfully long ways. I know for the airline industry they use fiber optics.

Each block station is tied into the railroad's telephone system. Those systems used to be wire-line, then they went to microwave and today are mostly fiber optic. Almost all long haul rail lines have fiber optic cable buried along the right-of-way that was installed by companies like Sprint, MCI, AT&T, etc. Most of the railroads either lease or own a few of the fibers in the cable that are used for the railroad's communication. It is a pretty good deal for the railroads, they don't have to maintain the cable that carries their traffic and collect lease money on the cable.

 

[poltergeisty]

Good info. Thanks for sharing!

 

[com501]

Multiple sites on a particular channel are 'toned' open by a DTMF code. Each radio on a particular frequency are voted at the hub. The dispatcher is shown visually which radio 'voted' the best signal and the voter steers the transmitter to the correct site. The dispatcher can also manually select the site, since the train is detected along the route through block occupancy detectors. The dispatcher knows exactly where the train is, how fast, and a whole slew of data about the condition of the train, also, including wheel bearing temps, number of axles, temperature where the train is, and other data scanned from RFID scanners along trackside.