(erielack) DL&W single-light signal heads

[Wdburt1_@_aol.com]

A single light, same size as all the others, in a round  target.  US&S 
called them an HC-33 marker light, IIRC.
 
Erie used them in a variety of applications, most commonly on  three-headed 
interlocking home signals that displayed only aspects where the  bottom or 
top signal head was always red.  Take a look at photos of Marion  or other 
complicated places and you'll see a few of those.
 
Erie never (so far as I know) accepted the idea of using a dark signal head 
 as part of a signal aspect.  A dark light was to be interpreted in the 
most  restrictive manner possible.  The DL&W did allow it, and made extensive  
use of darkened signal heads to convey various aspects.  For instance, some  
signals on the Scranton and Buffalo Divisions were set up with the marker 
light  below a standard, three-light color light signal head.  The upper head 
 could display red, yellow, and green.  If the upper head displayed yellow  
and the marker light came on displaying green, that changed the indication 
from  Approach to Approach Medium.  As you DL&W guys probably know, the  
railroad also made extensive use of two-over-two configured signals where the  
green light was on the bottom.  Some of these were used at  interlockings.  
In that application the only thing needed to convey Stop  was a red light 
burning in the upper signal head.  Add a green light below  it, and you got 
Medium Clear.  This configuration was also used in some  wayside signals to 
provide Approach Medium as discussed above.  In that  case one of the two 
lights in the lower target usually would be blanked  out.
 
 

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