Raytheon 138-119 Operator's And Service Manual page 31

Change Over Box
COMPASS
138- -119
STD22
If an error occurs in the DU1 of the compass system1, the DU 1 generates an error mess-
age "System Failure" , in terms of a 24 V DC switch potential, to the Change Over Box.
In the automatic mode this "System Failure" effects a switching--over from the outputs of
DU 1 to the outputs of DU 2.
The STD22 GG--R Gyro Compass System is equipped with a redundant power supply (see
section 4.3 Redundant Voltage Supply).
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Edition: April 06, 2005