Tone at beginning of transmission

[BM82557]

I've noticed some sort of tone initiates the conversation between trains and the dispatcher on 161.250. I hear the tone and the dispatcher responds "CSX dispatcher Baltimore answering" I've never heard a vocal transmission from a train start the conversation. Just curious as to what kind of system uses a tone signal like that and what the tone tells the dispatcher. The attached screenshot shows a typical example with the tone between the 2 vertical spikes on the left and the modulation on the right is the beginning of the dispatcher's response.

 

[slapshot0017]

CSX has a system of a dispatcher channel and a road channel on each subdivision, these vary from railroad to radilroad. The road channel will be used for calling signals and the crews talking back and forth. The dispatch channel is specifically used for the crew to talk with the dispatcher.

Mostly all railroads use this practice though. Instead of just blindly calling the dispatcher the engineer/Conductor will punch in a DTMF code to notify the desk that there is a train calling the dispatcher. Norfolk Southern uses this practice on the Harrisburg division so that their voter system can be used efficiently and the best line of communication can be used a.k.a. the closets control point with a radio tower.

 

[BM82557]

Thanks for the explanation.

 

[mikegilbert]

To add to what KD2BRR said, the tone you're hearing could be the system acknowledging the DTMF command. That is, once the system hears the correct DTMF sequence, the base station will emit a confirmation tone to let the engineer know his command hit the base station.

 

[emt603]

when the train or maintenance of way workers key in the DTMF tone for the tower they are closest too the VOIP gateway will recognize that tone and send an signal to the dispatchers console opening the squelch and telling the dispatcher what tower has been "rung up", after this info has made the loop the VOIP gateway will transmit a "ring back tone" telling the train crew or maintenance of way worker that the dispatch console has displayed there request to stand by for the dispatcher to answer. This used to be ran over regular POTS phone lines until about 2 years ago, now everything that I install and maintain for the class 1 railroad I work for is voice over IP on the company microwave network.

 

[slapshot0017]

Yes if there was any confusion with my Norfolk Southern explanation EMT hit it on the head.

Quick question if you work on the radio systems do you work for the railroads or a dealer? Trying to figure out a career path and I'm conflicted...

 

[motorola_otaku]

Quick question if you work on the radio systems do you work for the railroads or a dealer? Trying to figure out a career path and I'm conflicted...

All four of the big Class 1s do it in-house. Radio is a subset of telecom and most of the work is IT-related (including the radio network backhaul) so appropriate experience/certs are preferred.

KCS is kind of an oddball, they sub field work out to a company called Comet that's more or less a wholly-owned subsidiary.

 

[Project25_MASTR]

All four of the big Class 1s do it in-house. Radio is a subset of telecom and most of the work is IT-related (including the radio network backhaul) so appropriate experience/certs are preferred.

KCS is kind of an oddball, they sub field work out to a company called Comet that's more or less a wholly-owned subsidiary.

Oil field is very similar. The bigger companies have in house it/rf techs.

 

[rfradioconsult]

About half my career was spent in the oil patch, building and designing radio systems for domestic and international operations. Back then the large oil companies had their own tcom groups, I worked for a couple including Occidental.

 

[radioman2001]

Quote: "Quick question if you work on the radio systems do you work for the railroads or a dealer? Trying to figure out a career path and I'm conflicted."

Metro North presently has 9 openings in their radio department, also there are numerous openings in the camera and telephone divisions.

Go to MTA website and click apply for jobs.

Also some time ago about 1 year CSX was looking for a roving tech for the Tenn,Florida area.