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.

Wednesday, September 30, 2026

THORN Tower Just Won't Die

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Over the past few years I have been  reporting  on what turned into a  rather protracted   closure of Amtrak's THORN interlocking tower...
1 comment:
Sunday, September 20, 2026

NS Files to Replace Cab Signals with Back Door CBTC

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It was no secret that Union Pacific was planning to dismantle Norfolk Southern's significant cab signal territory that was inherited fro...
2 comments:
Monday, September 14, 2026

Amtrak Zephyr Trip Report: The More Things Stay The Same

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The last time I rode Amtrak's California Zephyr route was in 2017 just after there had been massive re-signaling over the Donner Pass, U...
Sunday, September 6, 2026

Amtrak Electrification Primer

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While this blog is dedicated to railroad signaling, I occasionally veer into the command and control of railroad traction power systems beca...
Sunday, August 30, 2026

I 'C' You - Caltrain Adopts SP Commuter Plates?

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In the bi-polar mess that are Union Pacific Signal rules , an often overlooked feature are the < C > plates that upgrade Advance Appro...
3 comments:
Sunday, August 23, 2026

NS Re-Signaling Old NKP West of Cleveland

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Although far less significant than recent re-signaling in core N&W territory, NS is currently going after routes that were last moderniz...
Sunday, August 16, 2026

Protecting Sharp Curves Before PTC

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Located at Milepost 90.3 on the former Rio Grande Moffat Tunnel route is a wonderfully analog system to help prevent inattentive train crews...
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Jersey Mike
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