Lighting Controls Blue Box LT Series Installation, Operation & Maintenance Manual page 66

66 THE BLUE BOX LT TROUBLESHOOTING WITH AN OSCILLOSCOPE
BUS SPLITTING TECHNIqUE
!
Note:To speed up troubleshooting when readings are
less than 200 Ω on the Continuity or Short-Circuit test,
refer to the "Bus Length Chart" on page 4 before splitting
the bus; this can provide an approximate distance to a
shorted pair or extra terminator from the test point .
1 . On the middle device of the bus, disconnect one Cat .
5 cable to create two smaller "half-buses" .
2 . Test each "half-bus" to find the side with the out-of-
range values .
3 . Repeat steps 1 & 2 on the out-of-range "half-bus, "
to create another "half-bus" until the cable, crimp or
device creating the out of range measurements is lo-
cated .
The idea is to split a bus in half and then half again – over
and over until the bad area has been located. It is also OK
to visually inspect each cable, crimp or device to detect the
problem.
Bus Checker Card
Bus Checker Card
Data/Power Jumper
Data/Power Jumper
Data/Power Jumper
Bus Checker Card