Railfan Technology > Morse code?? On the scanner

Hi. I'm presently on a railfan trip. On my scanner, and picking up the BNSF, I am getting what appears to be a morse code transmission at the end of the DS speaking. What is this? Thanks Chris uk.

Wait, wait, had that wrong. Fixed it:

The Morse Code is the repeater or network identifier. Morse code allows a somewhat technical person to turn it into the identification alpha-numeric characters. Other systems use a recorded voice. Some areas only require an identifier once a day, or similar, timing varies.

The identifier allows any interference with another system to be traced back to a Repeater installation. Interference could be due to higher than anticipated power levels at someone else's location, or atmospheric skip, bleeding through nearby transmission lines, harmonics or intermodulation products due to faulty equipment, etc, etc, etc.

There are also access codes to repeaters which sound like cell phone tones or similar. The access tones can be heard when an employee is 'toning up' a repeater before a discussion with the Dispatcher. The Repeater transmitter would simply time out to save power if needed, depending on design and location, etc.
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These days there are many ways to communicate, some of the Networks are dated but still worth keeping. Some of the other TO posters have more experience on Voice Repeaters than I have on, but that's the basic idea.

Enjoy your trip. Post'em if ya got'em.



Edited 3 time(s). Last edit at 10/08/25 22:52 by TCnR.

Thanks for the info. Much appreciated. Chris uk

Railroad remote bases usually don't use Morse "identifiers"  but repeaters may--those identifiers, when used, are often the FCC license no. associated with the repeater or base radio, transmitted in Morse code every so often. Also,  BNSF, and probably other railroads, still do have a few PBX channels that they use.  This offers the radio user--say, a MOW person, for example--radio access to the "land line" telephone system.  When the radio user "tones-up" the repeater or remote base with DTMF codes (often referred to by their old telephone trade name "Touch Tone" codes), the radio system connects to a land line where the radio user could dial a call using the radio's DTMF keypad.  This system predates cell phones and cell phones have pretty much replaced PBX communications, but railroads still may use PBX channels sometimes.

DTMF tones are also used in radio systems to "tone up" the Dispatcher, for example.  In DTMF, different tones represent, generally, the numbers 0-9, along with the "star" and "pound" sign.  In both "toning up" scenarios (PBX and Dispatcher call), a common practice is to use the star (*)  tone to bring up the remote base or repeater.  In the case of calling the Dispatcher, the Dispatcher desk that the radio user is trying to contact is the "console" of that Dispatcher.  So for example, if a train crew is trying to call Dispatcher desk (console) 125, the crew would tone up by entering "*125" on the DTMF keypad.  The radio system would then route that call to that Dispatcher console.  If one is monitoring the radio channel when the "tone-up" is made, one will hear the *125 sequence, followed by another tone a second or so later.  That following tone is transmitted by the radio system to let the train crew, in this example, know that the call was received by the radio system and is being routed to the Dispatcher console. 

Now, in PBX, things are more complicated.  Typically, the radio user will use the * key to tone up the PBX, then the user will enter another digit or two to indicate where they system should give the radio a dial tone.  For example, a radio user in town "A" wants to make a PBX call to a Supervisor in town "Z" a couple of hundred miles away.  The radio user would enter a DTMF number code (somewhat akin to an Area Code) that would direct the radio system to give the radio user a dial tone in town "Z", where a phone call would be a local call.  Then the radio user would call the Supervisor's phone no. as a local call.  This is where things get a bit convoluted.  The railroad radio system is semi-duplex, meaning that the radio user can not hear the response on the radio when the radio user has the microphone keyed.  Meanwhile, the "land line" phone system is full-duplex, where one can talk and listen simultaneously over the line.  So, the PBX is usually configured as a paired system, where the user is transmitting one AAR channel, while receiving on another.    The person on the receiving end of the call has to know to not talk while the radio user is talking because the radio user will not hear the recipient if the user's microphone is keyed.  Once the conservation is over, the radio user "tells" the radio system that the call has ended by pressing the DTMF # key.  If the user doesn't do this the PBX may hang open until the radio system times the call out and closes the PBX radio system.  I bring this up here as the PBX system would sometimes broadcast that Morse license no. sequence when the PBX system was closed after a call.  Crews were usually taught to "Star-up" and "Pound-down" to initiate then end a PBX call.  And, yes, those PBX calls could be heard by anyone monitoring the channel.  I knew train crews that got "brownie points" (demerits or disciplinary action) for using the company PBX to call their wives, girlfriends, etc. over the PBX, or--in couple of instances--to use the PBX to order and schedule a pizza delivery to a road crossing along their route.  In one of the latter instances, the train crew got in big trouble, not only for using the PBX for  "non-company" business, but also because the pizza delivery guy was late with the pizza, and crew's train blocked 7 road crossings in the town for 20 minutes while they waited for their pizza to arrive.  There was hell to pay for the crew on that deal.  That incident happened almost 40 years ago, long before cell phones, texting, and all the other "modern" stuff used for voice communications today. 

I have to tell one more PBX story.  One late evening, my scanner crackled with the PBX being toned up.  A brakeman on a certain train made what he thought was a pretty innocent call to his, uh, significant other (wife or girlfriend) just to let her know about what time that he would be off duty and get home.  She obviously did not realize that he was on the PBX where anyone, including plenty of other railroaders, could hear the conversation.  She went in to a long soliloquy about all of the fun things that she planned to do with him sexually when he arrived home.  This went on for for an inordinately long time before the brakeman could finally key up his microphone and say, sheepishly, "Honey, I'm on the PBX, everyone can hear us."  There was a long pause, then the sound of the land line hanging up.  The brakeman hit the # key to bring the PBX down.  I can only imagine the hazing that the brakeman got over that whole deal.  I never knew if any railroad officials had heard that call.  If they did, they likely figured that the grief that the brakeman would get from his fellow railroaders would be sufficient punishment.  I suspect that the brakeman did not receive the "welcome home" that his significant other had vividly described, either.



Edited 2 time(s). Last edit at 10/09/25 18:39 by WW.

Great info. Thanks.

Fascinating info on the PBX system. As one who used it from a train, I never did understand why we had to use 2 radio channels to make the system work, versus just a single channel for normal radio communication. The semi-duplex versus full-duplex explanation makes perfect sense.

In Northern California on the SP, and then into the UP era at least for some years until the system went away, we used 62-52 or 70-56 to access the system. Going off memories it was like *11 or *12 to activate the system. Once you activated the system you would get a dial tone just like on a land line phone. You would then press 8 if you wanted to call a number outside the railroad phone network or press 9 if you wanted to call a number in the company phone network. After that you would just dial the phone number like you would on a normal land line phone. Once you were done with the call you would press # and the same number you used to activate the tower. So say #11 or #12. This would then end the call, followed by the tower identification. I call still hear it in my head, "SP Mount Vaca out." Somewhere around here I have a cheat sheet that listed the various SP/UP radio towers in California and their respective radio channels with activation codes.

ble692 Wrote:
-------------------------------------------------------
> Fascinating info on the PBX system. As one who
> used it from a train, I never did understand why
> we had to use 2 radio channels to make the system
> work, versus just a single channel for normal
> radio communication. The semi-duplex versus
> full-duplex explanation makes perfect sense.
>
> In Northern California on the SP, and then into
> the UP era at least for some years until the
> system went away, we used 62-52 or 70-56 to access
> the system. Going off memories it was like *11 or
> *12 to activate the system. Once you activated the
> system you would get a dial tone just like on a
> land line phone. You would then press 8 if you
> wanted to call a number outside the railroad phone
> network or press 9 if you wanted to call a number
> in the company phone network. After that you would
> just dial the phone number like you would on a
> normal land line phone. Once you were done with
> the call you would press # and the same number you
> used to activate the tower. So say #11 or #12.
> This would then end the call, followed by the
> tower identification. I call still hear it in my
> head, "SP Mount Vaca out." Somewhere around here I
> have a cheat sheet that listed the various SP/UP
> radio towers in California and their respective
> radio channels with activation codes.

We still have a couple PBX installations on CSX....they hardly ever get used....