Raytheon 138-119 Operator's And Service Manual page 47

6.2 Gyro 2 fails
If Gyro 2 fails (not selected as heading sensor) a "silent alarm" is generated.
It means that the Gyro 2 is indicated as "failed" at the Operator Unit, but there is no acous-
tic alarm.
The error message "Gyro 2 Failure" can be detached from the Distribution Unit and
forwarded to external alarm devices (detached from the Change over Box too -- if con-
nected).
After repair the "silent alarm" is cancelled.
6.3 Distribution Unit 1 fails
The Change over Box switches over to the Distribution Unit 2 at once. The release of that
switching--over is the generation of the error message "System Failure" from the Distribu-
tion Unit 1. It means that the outputs of Distribution Unit 2 are forwarded from the Change
over Box.
This fail is not displayed at the Operator Unit.
An external connected alarm device shows the message "System Failure".
6.4 Distribution Unit 2 fails
The system stays in the actual operation mode. The active Distribution Unit 1 controls the
system.
This fail is not displayed at the Operator Unit.
An external connected alarm device shows the message "System Failure".
3769DOC000002
Change Over Box
138- -119
41
COMPASS
STD22
Edition: April 06, 2005