ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
MATERIEL USED IN CONJUNCTION WITH MAJOR ITEM
(2) Horizontal circle housing. The horizontal cir-
5-1. General. The Position and Azimuth Determining
System Test AN/USM-427 is used to test the PADS
cle housing contains the horizontal circle, the vertical
axis assembly, prisms for illuminating and reading the
computer, CDU, and IMU. Its operation is described in
horizontal circle, contacts and connections for electric
TM 5-6675-238-14. Marine Corp users shall refer to TM
illumination, and three spike feet for securing the
08839A-14/1
theodolite to the tribrach. The following items are
a. The Power Supply Test Set AN/USM-428 is
located on the horizontal circle housing:
used to test the PADS power supply and computer
power supply. Its operation is described in TM 5-6675-
(a) Circle-setting knob and cover. The circle-
309-14. Marine Corp users shall refer to TM 08840A-
setting knob, which is located on the side of the hori-
14/1.
zontal circle housing, is used to rotate the horizontal
circle to any desired position. The cover of the circle-
b. A Wild theodolite T-2 and target set are re-
setting knob is provided to prevent the operator from
quired for IMU alignment. Their operation is described
disturbing the orientation of the horizontal circle by an
below.
accidental touch. The cover should be closed at all
times except when the horizontal circle is being ori-
ented.
(b) Horizontal circle illumination mirror. A
a. The theodolite T-2, roil-graduated, is used to
hinged, tilting mirror to illuminate the horizontal circle
measure angles for PADs alignment. The theodolite,
is located on the lower portion of the horizontal circle
ving only one spindle, is a direction-type instrument.
housing. The intensity of the light on the horizontal
t has interior scales which are read by a built-in optical
circle can be adjusted by rotating and tilting the mirror
system. The scales, graduated in roils, are readable
until the circle is properly lighted. For artificial illumi-
directly to 0.002 mil and by estimation to the nearest
nation, this mirror is removed and replaced by a plug-in
0.001 roil. The scales may be illuminated by sunlight or
lamp.
by a built-in wiring system using artificial light. All
components of the instrument which can be seriously
(c) Instrument support lugs. Three rectangular-
damaged by dust or moisture are enclosed.
shaped instmment support lugs uniformly spaced
around the base of the horizontal circle housing. These
b. The theodolite is used with a canvas accessory
lugs are used to secure the theodolite to the base of the
case containing diagonal eyepieces for the telescope and
carrying case. The plug-in socket, which received the
reading microscope, a sun filter, a jeweler's screwdriver,
battery box cable for artificial illumination, is located
two adjusting pins, a camel's-hair brush, a plastic instru-
.
immediately above one of the lugs.
ment head cover, two lamp fittings for artificial illumi-
nation a battery case containing lighting devices and
(3) Alidade. The alidade is the upper (rotating)
spare bulbs, and a universal tripod with a plumb bob,
part of the theodolite. It includes the telescope and
plug-in sleeve, and tripod key in a leather pouch at-
microscope assemblies and the two standards that sup-
tached to the tripod. The accessories of some models of
port them, the vertical circle housing, and the horizon-
the theodolite are stored in the base of the carrying
tal clamp assembly. Located on the alidade are the
case.
following
(a) U-standard assembly. The U-standard as-
sembly forms the' support for all the components mak-
(1) Ttibach. The tribrach is that part of the
ing up the upper part of the instrument and includes
theodolite which contains the three leveling screws and
the horizontal circle axle and flange, the circle selector
e circular level. The leveling screws are enclosed and
knob and prism, and the horizontal axis prism.
dustproof. On models manufactured subsequent to
1956, the tribrach is detachable. On these models, the
(b) Levels. The theodolite has a plate level and,
a vertical circle level (split bubble) in addition to the
tribrach is secured to the theodolite by three tapered
circular level on the tribrach. The plate level is located
locking wedges controlled by the tribrach clamp lever.
at the bottom of the opening between the standards and
An optical plumb system is located in the tribrach for
is graduated to aid the operator in the precise leveling
accurately centering the theodolite over a station.
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