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Fri Jul 14 12:37:25 EDT 2017


In all my years studying CTC and their machines (since 1940s) and spending over 600 hours watching, helping and finally taking the place of a dispatcher at a CTC board at the CRR/CSX office in Erwin TN (1977-1991), I never once heard/read about the signal numbers being determined by the distance (inches) from the left side of the board.  Yes, normally they started with 2 (or 4 on the CRR) and skipped sequence whenever a space was left empty (for later changes) and yes, these locations were 2” apart on the board, but to my knowledge, the numbering had nothing to do with “inches.”  I could be wrong on this, and if so I apologize. 


Other than this minor issue, my article on signaling was enhanced once again by Larry Evans’ material and your selection of photos.




From: Kevin EuDaly [mailto:keudaly at] 
Sent: Thursday, July 13, 2017 7:57 PM
To: Glenn Fisher
Cc: nw-mailing-list at
Subject: Re: ERROR!


Hi Glenn:


            Well, I’ll have to respectively disagree.  The signal numbers were directly related to the panel from which they were associated, and they numbered them on two-inch centers beginning with 2 and proceeding across the panel.  They then named the signals according to which lever on the panel they corresponded with.  Sometimes groups of signals were covered with one lever — often a “28L” or “28R” lever on the panel could throw any number of signals depending on the setup out on the railroad, and many times there is sub-grouping in the relays behind the panel that control which signal is activated. If a number location on the panel didn’t need a lever, they skipped it and also skipped the two-inch number that would have been there.  If you look at the panel on age 14, you can see they skipped “170” because they didn’t need a lever on that two-inch center location.  Why would a signal department specify a skip in the numbers that always corresponds to the two-inch panel location?  Answer: They wouldn’t because the panel dictated the signal and switch numbers.  The signal department didn’t come up with the numbers and then Union Switch & Signal build the board to match, it was vice-versa.  

            You’re right, the “R” has to do with the direction it has to be thrown to affect that signal, as there can obviously be a corresponding 28L signal.  It’s the “28” part the caption refers to as being from the left side of the control panel (we read left to right), not the “R” as being “to the right.”  

            Actually, flipping 28 to the left wouldn’t affect the 28R signals at all (except to interlock them to “stop"), but would throw the signals facing the other way (and labeled 28L out on the railroad) to a more clear indication.  Interestingly, the operator can’t tell exactly what the signal says, only that it’s either “stop” or “not stop”.  He can infer the signal given based on how far he’s cleared the train, but can’t see that anywhere on his board.  Many railroads used very specific signal indications that an operator would never know, such as a green over yellow.  Also, some railroads used speed signaling (according to the rules the signal indication only told the engineer how fast he could run — i.e. a red over green indicating “proceed at 40 mph") and others used route signaling, where the signal indication actually indicated the route (i.e. a red over green being a “diverging clear” signal).  

            I don’t think many railroads actually labeled the signals with the corresponding lever locations on the board as seen in the photo, though that made it convenient for conversation.  They rather referred to the signals by location (and many were labeled with milepost numbers).  So a crew could tell the dispatcher, “I’m looking at a stop signal at Boaz.”  Also interesting is that when we run on Dad’s O-scale C&O railroad (which uses a real Union Switch & Signal board that came off the SP and was re-purposed to his C&O railroad), those of us that dispatch know which signals out on the railroad correspond to which levers (because we not only dispatch but run trains, too).  We then have an advantage in that we can call the dispatcher and say “I need 28R to move east.”  The C&O never put those lever numbers on their signal masts that I know of.  Because Dad’s part of the C&O is all east-west, throwing a signal to the right (an “R” signal) will always clear for eastbound movement, and to the left will always be for westbound moves.

            The caption looks correct to me.  

Kevin EuDaly
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PO Box 48, Bucklin, MO 64631
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On Jul 13, 2017, at 5:53 PM, Glenn Fisher <springhouse19 at> wrote:



I was shocked to see the caption on the top right side of page 17 in the latest issue of The Arrow.  The explanation of the number “28R” on the signal shown there is completely false.  The three signals at this location guarding the end of a passing siding are all numbered “28”, a number selected by the signal department that has nothing to do with distance (inches) from the side of the panel.  The “R” refers to the direction the operator must flip the lever on the CTC panel to clear that signal.  The two signals governing movement on the main line and coming off the siding are both numbered “28L”.  Flipping 28  lever to the Left would  clear one of those signals depending upon whether the switch was in Normal or Reverse position.       


I hope none of the readers would think that I was the cause of that error.


Glenn Fisher

Author of the article. 


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