General Information:

PRR Position Light Signal System - By the Philadelphia Chapter of the Pennsylvania Railroad Technical & Historical Society.

Pennsylvania Railroad Signal Drawing Symbols - Based on PRR Document S-601-A, 1935  - By Henry J. Sundermeyer.

Pennsylvania Railroad Position Light Signal Rules - Based on 1956 Book of Rules  - Excellent Java app that demonstrates rules vs. signal aspects. By Henry J. Sundermeyer.

NORAC Signal Aspects Chart - Dated 1993, but still is a reference for Pennsy PL signal aspects!

The Position Light  - A blog devoted to explaining the ins and outs of North American railroad signaling, past, present and future. Some excellent PRR coverage!


Tower Photos

Interlocking Diagrams

Union Switch & Signal (US&S) was a primary supplier of control systems to the Pennsylvania Railroad. Their compact, desktop series of CTC machines were labeled the 500 series. What follows is a discussion of what is seen on these machines and how they differed from location to location.

Our first subject is the machine that was installed in ALTO tower (Altoona) to remotely control WORKS, ROSE, HOMER, and ANTIS. It features 30 vertical spaces. Below is the right half of the machine.

ALTO CTC machine right