The Japanese Signal Lamp is a portable, lightweight field unit
designed for point-to-point communication on the ground by means
of a keyed light beam.
It is powered by a hand-driven generator, weighing 13 pounds. The
complete unit, less tripod and generator, is carried in a plywood
case with metal edges the over-all dimensions of which
are 10 3/4 x 8 1/4 x 5 3/4 inches. The
unit weighs 10 pounds, including the carrying
case. Aluminum is used extensively both in the lamp and accessories. The
lamp and the carrying case are painted brown.
The under side of the plywood case cover contains a manufacturer's
nameplate and a list of parts. The principal parts are: signal lamp,
lamp mount, shutter, telescope, two telescope filters (one red and one
yellow), occluder, lamp filter case, three lamp filters (red, yellow, and
blue), six lamp bulbs, lamp bulb box, key and cord, tripod, carrying
case, generator (hand-driven), hand crank for generator, wrench.
The lamp beam can be directed to a definite point of known
elevation and azimuth by means of a tubular peep sight, an elevation scale,
and an azimuth circle. The tubular peep sight is factory-aligned with
respect to the beam and is fastened to the lamp housing by means of
screws. The elevation scale is graduated in hundreds of mils from
-1600 to +1600 although vertical travel is possible only between the
limits of -1340 to +1360. The azimuth circle is graduated in hundreds
of mils from 0 to 6,400, with five divisions of 20 mils each
There is evidently a telescope mounted on top of the lamp (the
telescope was missing from several samples of the equipment
examined, doubtless a sacrifice to souvenir hunters). It is apparently
used to align the lamp and to aid in receiving messages flashed from a
distant sending lamp.
The maximum range of the lamp is estimated to be 5 miles on a
clear day. The maximum signaling speed is four words per minute.
A shutter over the face of the lamp varies the beam produced from
a cross to a single dot in seven stages. The operator selects the
desired shutter opening by moving the numbered slotted spring
catch located on the face cover.
The parabolic reflector has a face diameter of inches, is highly
polished and is protected by a coating of clear lacquer. The bulb
used is gas-filled and requires 2.5 amperes at 6.2 volts. It is focused
by bringing the filament in line with two peepholes on the side of the
signal lamp housing. The bulb socket is mounted on an adjustable
horizontal arm inside the lamp housing to permit focusing.
A. pivoted worm drive is used to disengage the gears for rapid
rotation of the lamp. The same pivoted worm drive is used in the elevation
arm for rapid vertical movement.
|Japanese signal lamp and generator, unassembled, showing
carrying case, lamp components (minus telescope and tripod) and generator.|
The electrical circuit of the lamp includes the resistance of the key
and cord. It is inferior to that of the U.S. Signal Lamp Equipment
EE-84 in which keying is accomplished in a local circuit, operated
through relay contacts, that excludes the resistance of the line between
the key and the relay from the lamp circuit.
Electrical connections to the bulb assembly terminate in a two-pin
female socket located on the side of the lamp housing. The generator
and key are connected to this female socket by a length of two-conductor
wire terminated in a two-pin male plug. The key is a
simple make-and-break key encased in a wooden box.
The hand generator is contained in a wooden case and is provided
with a folding iron stand for operation from a sitting or kneeling
position. The hand-crank motion is transmitted to the armature
through a spur gear train and must be operated at 60 revolutions per
minute in order to produce rated output capacity of 3.5 amperes at
6.5 volts. A cut-out shunts a load resistance across the output when
the potential reaches standard voltage.
To power the lamp, however, any 6-volt d-c source can be used.
Four U.S. Signal Corps batteries BA-23 connected in series are recommended.