RAILROAD SIGNALS of the U.S.

"DOMINO" SIGNALS

In the 1920's, a new style of signal was born out of necessity.  These signals were installed as part of the upgrade in the signaling for the soon to be completed Chicago Union Station. 

The station designers did not want 24 foot high semaphore poles blocking the view of the many beautiful overpasses, not to mention that the overpasses were spaced about 800 feet apart, so a locomotive engineer would have difficulty in seeing the upper signals.

This signal is a variation of the Pennsy PL (Position Light) signal.  The background is 4'-2" square, and uses the same equipment as a PL signal.  Instead of placing the heads equidistant from the center (18"), as on the Pennsy, the top and bottom middle heads were placed in line with the outer two, giving the signal it's square shape.  In addition, the aspects of two signal heads were now displayed on one.  Another variation of this signal can still be found in Northumberland PA.

I would like to thank Mike Spencer for the use of his photos, as he has one of the few units still surviving from when they were taken out of service (I think) back in the late 80's.

  Clear                 Approach                 Stop

  Restricting       Slow Approach

Created 11/8/06
Last Modified: 31-Jan-2010