The Position Light

A blog devoted to explaining the ins and outs of North American railroad signaling, past, present and future. This blog seeks to preserve through photo documentation the great diversity and technical ingenuity of 20th century signaling and interlocking hardware and technology. Related topics cover interlocking towers and railroad communications infrastructure.

Note, due to a web hosting failure some of the photos and links may be unavailable.

Tuesday, July 7, 2026

Caught on Camera: Clear to Next Interlocking for UP #4014

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For much of the  Union Pacific Big Boy  2026 Coast to Coast excursion tour, #4014 was able to operate like any other Class 1 main line locom...
Monday, June 29, 2026

LIRR Greenport PTC - Much Ado About Nothing

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We have another data point regarding the FRA's PTC paranoia, this time regarding the Long Island Rail Road's Greenport Branch waiver...
Sunday, June 21, 2026

Amtrak THORN Tower to Close Aug 8, 2026

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For over a year I have been tracking the slow motion closure of Amtrak's THORN interlocking tower . located on the old PRR Main Line ...
Sunday, June 14, 2026

Art's LIRR Archives Online...For Now

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 Word on the street is that the street is that the person behind Art's LIRR Archives , Art Huneke, has recently passed away. While not q...
Sunday, June 7, 2026

Yes, US&S Made Handguns

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In the past I have spoken to the importance of looking for the Union Switch and Signal label when purchasing your next M3 switch machine. H...
Sunday, May 31, 2026

Caught on Camera: Track Circuits and Electrification Current

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In a previous post covering the phenomena of a "bobbing" track signal that cycles intermittently between one or more states. I mo...
Friday, May 22, 2026

MARC's Empty ACSES Bracket

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In 2020 MARC moved to switch from Amtrak's ACSES transponder based PTC system to the ETMS system used by freight railroads that is more ...
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Jersey Mike
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