GRESHAM JCT's Sequence Switches Explained

 Years ago I wrote up a profile of METRA's GRESHAM JUNCTION tower on the Rock Island division south of Chicago.  Not only had GRESHAM JUNCTION managed to stay open into the 21st Century, it was a unique North American example of a sequence switch interlocking. Supplied by the Standard Telephone and Cables Company of London, the interlocking used telecom grade sequence switches to carry out the interlocking functions instead of relays.

In my original post I provide photos of the equipment as well as a general concept of how sequence switches work and some sequence switch interlocking circuit diagrams from the UK, but without time and access to the equipment or someone who was intimately knowledgeable about how it functions, my commentary had to remain at a very high level.  Fortunately, the gang from the Connections Museum in Seattle is on the case because sequence switches is pretty much how Bell Number 1 Panel central office machines functioned (again, as opposed to later relay based technologies). I could try to go into things, but fortunately the museum's YouTube channel has video that is specifically about how sequence switches work. 

Once you see them in action at the Connections Museum, their function in the photos from GRESHAM JCT will become obvious. Of particular note is the function of the magnetic clutch mechanism that rotates the switch spindle. Perhaps if I stare at things enough I can determine what each sequence switch corresponds to in the interlocking.  Is each a complete route? An entrance? An exit? An entrance-exit combination? Let me know in the comments if you figure it out.  BTW, if you like this video take some time to watch the rest of the Museum's content.  It's top notch and does a superb job of explaining some normally opaque topics in the realm of pre-modern telephone switching technology.

CSX Bags Guilford But When to Expect Change?

CSx is set to complete its purchase of the former Guilford Rail System (currently branded pan Am Railways) on June 1, 2022.  However does this mean to immediately expect the end of NORAC Rules, searchlight signals and bracket masts? Well according to some initial reports the community will enjoy at least a slight reprieve before CSX has the opportunity to go to town on the Boston and Maine's legacy.

Guilford searchlights and the Lowell Wye.

As of now CSX plans to make no changes to former Guilford operations until October, 2022 due to the existing collective bargaining agreements and delays to the sale of the Pan Am Southern joint venture to a G&W subsidiary.  This means NORAC Rules and signal indications will remain in service until that point and it is unlikely that CSX will embark in any large scale re-signaling investments. CSX will also need to improve/signal the line between Worcester and Ayre to actually connect the former Guilford Freight main Line with its former Conrail Boston Line.

Boston Line CP-45 at Worcester

In the longer term, use of Rule 562 cab signal without fixed wayside signals on both the former MBTA territory as well as the Boston Line will likely keep the former Guilford territory under firmly under CSX's legacy "Conrail" signal rules, even if the operating rules change. How PTC is integrated into the new territory remains to be seen as MBTA lines that share the former Guilford Freight Main Line route around Lowell, Ayre and Haverhill, will be ACSES and cab signal equipped. It is entirely possible that CSX will choose to complete the look and install 562 between Worcester and Ayre and as part of any re-signaling projects on the Freight Main Line, including the Downeaster corridor north of Haverhill. 

Boston Line CP-187 with Conrail Small Target Searchlights

 As has been observed on the Boston Line, Darth Vader type signals have been slowly supplanting those of Conrail vintage, however this process is not complete after 20 years due to the young age of the vintage Conrail signaling. Fortunately the former Pan Am Southern covers both the Freight Main Line to Mechanicville, NY and the CT Valley Line used by Amtrak. The latter was recently re-signaled in the Guilford style with the remainder getting a mix of Darth Vaders and Guilford signals in any re-signaling projects.  I suspect the orphan nature of this route will further stunt investment, hopefully prolonging the life of the remaining B&M vintage searchlight equipment and US&S pulse code CTC .

Montana Rail Link Loses Its Lease

This news isn't exactly new, but I figured I should go over the signaling implications of the end of Montana Rail Link's lease of 400 miles of former BN Main Line in the state of Montana. 

Classic Northern Pacific Searchlit Cantilever Mast on MRL

MRL is fairly special in that it runs a high quality CTC main line with modern motive power such as SD70M-2's.  Like many regional railroads with signaling, changing out its legacy equipment was never a high priority, especially since it was PTC exempt and the the physical plant was leased not owned.  MRL's former Northern Pacific/Burlington Northern trackage is largely signaled with searchlights and GRS Type D color light signals with a mix of masts, small vintage gantries and cantilevers. 

BN vintage GRS Type D masts on MRL

MRL was in the process of having many of its legacy signals replaced by BNSF standard Darth Vader types with relay box mast combos being a popular replacement choice.  The reversion to BNSG is likely to accelerate the replacement process and although BNSF could in theory try and get a PTC exemption if it does not need to run TIH cargo on the line, provisions to make the route available for some potential passenger services make the prospect of government infrastructure money highly likely and with that comes a brand new bland signal system sooner rather than later.

Brand new BNSF type Darth Vader type signals newly installed on MRL.

As of this writing the lease termination appears to still be under review and if the limbo state accelerates and decelerates the existing re-signaling efforts remains to be seen. I recommend anyone in the area to get their photos now, the more the better.

Union Pacific to Abandon ATC and ACS Effective June 1, 2022

 Well after about 18 months of regulatory approval, Union Pacific is set to remove all mention of the CNW Automatic Train Control and more general Automatic Cab Signals from the rulebook effective June 1, 2022.  As explained before the legacy CNW ATC system was super clunky and was definitely not worth keeping in the face of PTC.  The ACS seems to be more of a cost cutting move as coded track circuit cab signals can compliment ETMS PTC as demonstrated by Norfolk Southern.  However Union Pacific's cab signal implementation had some shortcomings that would have likely required additional modifications to make a joint ACS/ETMS system work well. Anyway, the real loser are the Employee Timetables which are set to lose a substantial amount of their color palette.

It was mentioned that Union Pacific will still require ACS equipped lead locomotives in some areas, which I am assuming is the Hiawatha Sub as that served as Union Pacific's "Rule 562" experiment and lacks wayside signals. The Hiawatha has Aspect Change Points every 1.5 miles, in line with the PRR/Conrail/Norfolk Southern practice. It is also important to remember that in most cases the ACS codes will remain in the rails as they are used to transmit block state.  Engines will either just run over the territory with their ACS fully inoperative or simply not present. Anyway, if you want a copy of the current UP Rulebook with the ACS and ATC sections intact, download it from the official site now. If you're reading this in the future, I saved a copy of the final revision with the ACS/ATC material.