TM 5-6675-250-20
1 - 1 1 . T E C H N I C A L P R I N C I P L E S O F O P E R A T I O N ( C o n t i n u e d)
b .
Electronic Control Unit (ECU)
(1)
(2)
(3)
(4)
(5)
Panel illumination control (1).
E n a b l e s t h e o p e r a t o r t o i l l u m i n a t e t h e p a n e l d u r i n g n i g ht
use. During day operations the control is rotated fully counterclockwise. To illuminate the
panel for night operations, the control is rotated clockwise.
Mode select switch (2).
The MODE SELECT switch is maintained in the PWR OFF position
when the equipment is not in operation. Placing the switch in THEO ILLUM position lights
the telescope reticle, the scales and the autocollimation eyepiece. Placing the switch in the
S E L F T E S T p o s i t i o n e n a b l e s t h e o p e r a t o r t o p e r f o r m a s s u r a n c e t e s t s o f t h e e q u i p m e nt
b e f o r e a n d d u r i n g o p e r a t i o n . T h e d e t e r m i n a t i o n a n d s e t t i n g o f b i a s c o n d i t i o n s i s a c c o m-
plished with the use of the MODE SELECT switch in the BIAS position. Placing the switch in
GC (gyro compassing) applies power to the gyro motor and indicates the alignment opera-
tion of the instrument. Through the BRAKE ON position, the gyro motor is stopped when it
i s d e s i r e d t o r e p e a t a l i g n m e n t s o r s h u t d o w n t h e i n s t r u m e n t . W i t h t h e M O D E S E L E CT
switch in the THEO ILLUM position, all system power is off except to the theodolite. In this
mode the theodolite may be used for determining azimuths from the original north determi-
nation, but the azimuth should be verified by rereading to the target after caging and brak-
ing of the gyro wheel. In this mode the theodolite can also be used for any normal theodolite
p r o c e d u r e.
Power on indicator (3).
The application of power to the system is indicated by the illumina-
tion of the PWR ON indicator. Failure of the indicator to light when the ECU is connected to
t h e p o w e r s o u r c e , a n d w h e n t h e M O D E S E L E C T s w i t c h i s m o v e d f r o m t h e P W R O F F or
THEO ILLUM positions, indicates a malfunction in the system.
Press to test switch (4).
Press to obtain a TEST METER indication for each test position
setting of this TEST SELECT switch. Operation of the PRESS TO TEST switch is needed only
during the self-test procedure to obtain an indication on the TEST METER.
Test select switch (5).
Used in conjunction with the TEST METER to check subsystems of
the equipment and stages of operation. During self-test operations, the selector switch is
placed to each of its positions; at each position the PRESS TO TEST switch is pressed and
operability of the associated circuit is indicated on the TEST METER (pointer in green area
for all but SOURCE VOLTAGE, which is displayed on the upper meter scale and GYRO,
which should center in yellow area).
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