Hooded signals and related questions.

[enginewhistle]

One thing i've been wondering for some time now, when did those hooded safetran signals first start being used on railroads? I saw some get installed in my town about 2005 and I saw a picture of an abandoned hooded signal at Minturn, Colorado on the old Tennessee Pass line.

Mainly a surveyor question, but what does LD and RD mean on signals? (Example: Searchlight Signal 06 RD)

 

[JIb228]

RD and LD Stand for Right Diverging and Left Diverging. If you have a turn out and the main line goes left, and the siding is right, place a RD. If the siding is left and the main is right, place a LD.