The Pennsylvania Railroad used a position light signal system that somewhat simulated the blade(s) of a semaphore.

Rule	Aspect	Name	Indication
280		Clear Block	Proceed; for passenger trains, manual block clear; for trains other than passenger trains, manual block clear outside of yard limits.
281		Clear	Proceed
281B		Approach Limited	Proceed, approaching next signal at Limited Speed.
281C		Limited Clear	Proceed, Limited Speed within interlocking limits.
282		Approach Medium	Proceed, approaching next signal at Medium Speed.
283		Medium Clear	Proceed, Medium Speed within interlocking limits.
284		Approach Slow	Proceed, approaching next signal at Slow Speed. Trains exceeding Medium Speed must at once reduce to that speed.
285		Approach	Proceed prepared to stop at next signal. Trains exceding Medium Speed must at once reduce to that speed.
285A		Caution	Trains exceding Medium Speed must at once reduce to that speed. Where a facing point switch is connected with the signal, approach that switch prepared to stop. Approach next signal prepared to stop.
286		Medium Approach	Proceed at Medium Speed prepared to stop at next signal. (bottom aspect is flashing)
287		Slow Clear	Proceed, Slow Speed within interlocking limits.
288		Slow Approach	Proceed prepared to stop at next signal. Slow Speed within interlocking limits.
289		Permissive Block	Block occupied; for passenger trains, stop; for trains other than passenger trains, proceed prepared to stop short of an obstruction, but not exceeding 15 mph.
290		Restricting	Proceed at Restricted Speed.
291		Stop and Proceed	Stop, then proceed at Restricted Speed.
292		Stop signal	Stop

Notes:
On signals with a bottom head that bottom head may or may not have a glare-shield (background) or may have a partial glare-shield.

Created 05-10-2007
Updated 05-19-2007