A section of a screenshot of the Dispatcher's Display.
November 01, 2007 Every railfan at some point in life has been trackside without a scanner just hoping for a train, heck anything, to come by. You decide to leave for the day, and while sitting at the stoplight at the adjacent intersection, a train comes rumbling by. So you vow to yourself NEVER to leave home without your scanner and you watch train after train rumble by without necessarily hearing them or the dispatcher. This is where ATCS monitoring comes in. So what is it?
ATCS monitoring is based on being able to monitor a railroad's CTC control points IF they are broadcast over RADIO code line. Two components of any radio code line are the "BCP" (commands from a field center), and the corresponding "MCP" (actual wayside device at the control point) that transmit information back and forth. BNSF is the only railroad in the Twin Cities that actually broadcasts over radio code line. UP, CP, MN Commercial and others do not on their control points. There are various protocols of radio code line in the U.S., with BNSF using a particular one in the Twin Cities. ATCS monitoring does not provide information about the trains or engines themselves. It does provide information regarding switch position, east and west signals, and approach blocks to a control point itself. That's the background knowledge. So how do I do it?
You notice above the word "radio" is capitalized. That's where the scanner comes in. Scanners process incoming sound through discriminator tap circuitry so that we can "hear" voice communication. By a minor modification of the scanner's discriminator tap we can "hear" raw audio coming into the scanner. If you are near BNSF trackage, tune to 161.010 and you will hear data bursts that sound like a fax machine. By connecting the scanner to a computer, and using the ATCSmonitor software, these data bursts are decoded and populate a man-made dispatcher display. The DS display shows nothing more than occupied track segments (displayed in red) and proceed signals (displayed in green). Long story short, you won't see WHAT the train is, but you will see exactly WHERE the train is. You now don't have to rely on your voice scanner
Now if you don't own a scanner, don't worry. Thanks to the efforts of myself and others in the area, there are currently four servers of live feed from antennas at houses being broadcast. They are received through an internet connection.
Finally, you may be asking yourself "Are the railroads ok with people knowing this information?" ATCS software is a read-only application and users can have no impact on actual field conditions. An open letter to the railroad industry can be found here: http://www.atcsmon.com/relax.html.
That is the basis of ATCS monitoring. Feel free to contact me with any questions.
Additionally, here are some references for more reading:
-Nat
Editor's note: This begins a monthly series of articles about this great railfan tool. Nat has been instrumental in making available the schematic for the Metro area. I, like many of you, am interested in ATCS but know little about it. I had dabbled with the software, but never got much further than installing it and watching packets scroll by. Stay tuned for more introductory articles and "Tips of the Month" as this series unfolds.