ETC Obsession User Manual page 267

Chapter 21 Accessories
LEDs
Two LEDs labeled A and B are located in the upper left corner of
the consoles' face panels. The chart explains their meaning.
Console A is main
Console B is main
Tracking off
Tracking interrupted,
A is main
Tracking interrupted,
B is main
A console B console
A LED B LED A LED
on off off
slow off off
blink
off off off
fast off off
blink
off off off
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B LED
slow
blink
on
off
off
fast
blink