The signaling shutter is a venetian blind shutter
1. Tip the rear end of the searchlight up to its
mounted inside the drum behind the front door. It is held
highest position and lock it in place.
in the closed position by two springs and is manually
2. Release the clamp ring toggle and remove the
opened by a lever on either side of the drum. The
clamp ring (fig. 4-27).
parabolic metal reflectors mounted on the inside of the
3. Remove the backshell assembly by raising it up.
This will disengage it from the hook and tab.
The lamp is usually a 1,000-watt, 117-volt
4. Pull the gasketed lamp out of the shutter adapter
incandescent lamp having special concentrated
assembly by gripping the lamp gasket on its
filaments that reduce the area of the light beam. The
periphery and lifting it out. This will disengage
lamp is mounted in a mogul bipost socket. The socket
the gasket lugs from the notches in the adapter
is located in front of the reflector and can be adjusted
only slightly. The replacement of the lamp is
To replace the lamp in the housing, take the
accomplished through the rear door of the search-
1. Make sure that the word TOP marked on the
12-INCH MERCURY-XENON SEARCH-
lamp is aligned with the word TOPon the gasket
L I G H T S . -- Some of the older mercury-xenon
and that the lugs of the lamp are firmly seated in
searchlights are 12-inch incandescent lamp searchlights
the recesses provided in the gasket.
converted to use a 1,000-watt compact mercury-xenon
2. Make sure that the lugs are set into the notches
arc lamp. The addition of a small amount of mercury to
in the adapter assembly located inside, and at the
the xenon gas produces a much more brilliant light with
rear of, the shutter housing.
a great deal of radiation in the green and ultraviolet parts
3. Set the backshell assembly over the shutter
of the spectrum. The increases in light intensity greatly
assembly, engaging the shutter hook into the slot
increase the range of the searchlight.
of the backshell.
The modifications needed to convert the
4. Using the hook as a hinge, carefully swing the
incandescent lamp searchlights include installation
lower part of the backshell down to the shutter
of a lamp holder, lamp adjuster assembly, and lamp
assembly, engaging the shutter tab into the notch
in the rolled edge of the backshell. Be careful to
swing the backshell down in a straight line to
make direct engagement and to ensure proper
positioning of the lamp contacts on the terminals
of the lamp.
5. Replace the clamp ring, making sure that the
hinge pin is set into the notches of the adapter
and backshell assemblies.
12-INCH INCANDESCENT SEARCH-
LIGHT.-- The 12-inch incandescent searchlight is
used primarily for signaling and secondarily for
The searchlight (fig. 4-29) is comprised of the
mounting bracket, yoke, drum, and lamp. The mounting
bracket permits the searchlight to be secured to a vertical
pipe or to a flat vertical surface. The yoke is swivel
mounted on the bracket to allow the searchlight to be
rotated continuously in train. The steel drum provides
a housing for the lamp, and its trunnion is mounted on
the yoke so that it may be elevated or lowered Clamps
Figure 4-29.--A 12-inch incandescent searchlight.
are provided for locking the searchlight in any position
of train elevation.