The Union Switch & Signal searchlight signals are well designed and constructed.  They were widely adopted throughout the Western United States and many remain in operation today.

The Union Switch & Signal Company was founded by George Westinghouse in 1881.  In 1887 the Company moved from Pittsburgh, Pennsylvania to Swissvale, located just outside of Pittsburgh Pennsylvania.  It has recently located back to Pittsburgh proper.

The searchlight signal was invented by Thomas Hall in 1869, and variations on the original “banjo” design, which permitted a single light source to display three different colors, were manufactured by the Hall Signal Company through 1925, when the Company was acquired by Union Switch & Signal.

Searchlight signals display up to three different colors or "aspects" through a single lens. They do this by moving a colored filter or "roundel" into a light beam which is projected out of the unit. This complicated internal mechanism requires routine removal and calibration and is subject to mechanical failures. This is the primary reason these signals are quickly disappearing from the railroad lines. They do however, undoubtedly display the clearest and farthest reaching aspects.

Searchlight signals have a removable internal unit which generates the different colored light beams. The light and the position of the colored lenses are controlled by separate 12 volt electrical signals. When no voltage is applied to the lens position mechanism, the unit displays red. When voltage is applied to the mechanism, the unit displays green or yellow depending on the polarity of the signal. Thus, when power is lost, the most restrictive aspect is displayed.

H and H-2 Styles

H-5 Style

Ground and Mast Mounting

H Internal Unit

H-2 Internal Unit

H-5 Internal Unit

Close-up Prism

Phankill Unit

Odds and Ends

Restoration

Above.  Side view of mast mounted H-2 signal.

Above.  To open the rear door of the signal, the locking mechanism is loosened by turning the handle.  Once loose, the handle is used as a lever to disengage the hook from a catch mounted on the top inside of the case.  Note the rope gasket material used to seal the rear door.  These ropes were impregnated with wax to protect against moisture penetration.  Gaskets on modern units are made from neoprene, a synthetic rubber-like material used widely in automotive door seals..

Three photos above.  Style H-2 signal displaying red, yellow and green aspects.  The camera is positioned outside of the beam of the signal.

Above.  Open back of the style H-2 signal showing its internal unit.