Raytheon 138-119, Operator'S And Service Manual

Page: 11 / 55

COMPASS
STD22
Change Over Box
138--119
5
3769DOC000002
Edition: April 06, 2005
2 Principle of function of the Change Over Box
2.1 Principle “Change Over Box in the STD 22--System”
In the redundant system of the Standard STD 22 the Change Over Box and the Change
Over Switch are used to switch--over between the output signals of both systems.
The diagram below shows the principle of switching--over including the fault monitoring of
Compass system 1.
”A”
”B”
”C”
”A”
”B”
”C”
”A
In1”
”A
In2”
”B
In1”
”B
In2”
”C
In1”
”C
In2”
”Relay
C”
”Relay
B
”Relay
A”
24V
DC
”C
Out”
”B
Out”
”A
Out”
”Sy
st
em
Fai
lu
re”
Change
Over
Box
Change
Over
”Sy
st
em
Fai
lu
re”
”S
ys2”
”S
ys1”
”Automatic”
Compass
S
ystem
1
C
ompass
S
ystem
2
”D”
”D”
”Relay
D”
Switch
DU
2
DU
1
24V
DC
Figure 4: Principle of switching--over in the compass system STD 22