When a signal is located in a position were light can reflect off of the outer doublet, there is potential for “phantom” signals.  To kill these signals, a Phankill unit is often used.  Phankill units can be used on both ground and mast mounted signals.  These units are usually used with an inclined front cover glass which also helps reduce phantom signals by reflecting external light striking the outside cover glass downward.  The outer glass on an inclined cover can be clear, as that pictured, or it can have horizontal prisms running across the outside to spread the light exiting the signal upward by approximately 10 degrees.  This is useful with ground mounted signals.

The Phankill units and inclined cover glasses can be used with both H style and H-2 style searchlight signals.  Because the Phankill unit has an integral close-up prism, the outer doublet on the H should have a clear center or “bullseye” (i.e. no deflecting close-up prism).  On H-2 style signals, the close-up prism should be removed.

Above.  Ground mounted signal shown with Phankill unit mounted behind an inclined glass holder.  The short lens visor, which normally covers the top of the Phankill unit and the inclined glass holder, has been removed.

Above.  H style signal with Phankill unit, inclined glass and visor removed.  Note the special lens ring with internally threaded mounting studs and the outer doublet with a clear bullseye.

Pankilll unit underneath and inclined glass holder.  The glass has been removed.

Above.  View on left is the outside of the Phankill unit and inclined cover glass holder as shown (above left) mounted on the H style searchlight signal.  View on right is a cross section of this assembly showing the honeycomb of the Phankill unit.

Above.  Front view of Phankill unit and inclined cover glass after removal from signal.

Above.  Honeycomb Phankill unit with integral close-up deflecting prism.  The prism is adjusted by slightly loosening the inclined glass holder and rotating the entire Phankill unit under the inclined glass holder.