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SP LIGHTS

Photos taken at Portola Railroad Museum of the SP 2873 GP9

Photo source: March 1998 issue of "Trains". (permission for cropped photo: 2/20/98)
These are all Pyle-National lights on a GP9 Southern Pacific locomotive.
GE makes a PAR-56 sealed beam unit which is rated at 30 volts/200 watts. It is 7 inches in diameter.
This lamp unit is used for the headlights, ditch lights and the 20585 Gyralite.
Newer versions of this lamp include a 75 volt option which has the advantage of eliminating the voltage dropping resistors. (standard locomotive voltage is 72/74 volts)

The top-most light is a 17550 or 17770 Gyralite.

In going over the literature on this type of light, it seems that much of the distinction as to exact number in this series is based on the bulb type used together with the location of the conduit hole in the unit.
see text for details

The next and last twin fixture in this photo is a twin stationary headlight unit.

Note that the upper 2 gyrating warning lights are "back mounted" to the plate between the locomotive's number boards.

No. 3186 Southern Pacific GP9 with back mounted 20585 Gyralite and 17540-17570 Gyralite

No. 4317 Southern Pacific SD9 with a back mounted SBW-2-300 Mars Light and SBRE-100 Mars Light (top box type unit)
Photo by Ted Benson

No. 8891 Southern Pacific SD45 with flush mounted 20585 between the number boards and 17540-17570 Gyralite inset into nose