TM 5-6675-250-10
1-9. TECHNICAL PRINCIPLES OF OPERATION
a.
Gyroscopic Reference Unit (GRU)
(1)
Uncaged indicator (1). Illuminates during operations when the pendulum is uncaged.
Caging knob (2). Used to uncage the pendulum in the bias mode and after the gyro motor
(2)
attains synchronous speed in the gyro compass (GC) mode. Also used for caging the pendu-
lum after bias and after GC has been completed. Illumination of the GYRO SYNC indicator
on the ECU is necessary prior to activating the CAGE-UNCAGE knob when in GC mode.
Vertical lock (3). Permits operator to lock telescope at any desired vertical position. When
(3)
vertical lock is released (turned counterclockwise), the telescope is free to be moved to any
vertical position.
Elevation control (4). Permits operator to control vertical positioning of the telescope. The
(4)
control is used to center target image vertically in the reticle pattern of the telescope.
Horizontal lock (5). Permits operator to lock theodolite at any desired horizontal position.
(5)
The lock is released when it is necessary to rotate the theodolite; light finger torque is
applied to lock the theodolite at the desired position.
Azimuth control (6). Permits the operator to adjust the horizontal position of the theodo-
(6)
Iite. The control is used to center the target image horizontally in the reticle pattern of the
telescope.
Micrometer control (7). Permits the operator to adjust the full range of the vernier scale to
(7)
obtain an accurate horizontal and vertical scale reading.
(8)
Altitude level control (8). Adjusts the position of the altitude level and V circle (vertical)
optical scale.
(9)
Altitude level mirror (9). Manually adjustable to permit the operator to see the altitude level
without changing from a telescope and azimuth scale reading position.
(10) Theodolite scale lamp eyepiece (10). Used to view the optical scales. The eyepiece can be
swiveled to allow the optical scales to be viewed from any position.
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