B&K Precision 2542B-GEN - Manual - Manual (Page 183)

Arbitrary Waveform Generator
183
This is the generator’ s modulating waveform output. This
terminal also serves as as the external trigger input for the
oscilloscope. When Trigger Source in the Trigger menu is
set to EXT or EXT/5, this terminal will function as an external
trigger input for the oscilloscope. When it is set to all other
sources, it will function as the modulating waveform output
from the generator.