Philips PM3320 Operating Manual page 51

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4-31E
With NEGATIVE SLOPE off, the time base is triggered on the positive-
going edge of the trigger signal. With NEGATIVE SLOPE pressed (on),
the time base is triggered on the negative-going edge of the trigger
signal, which is indicated by the built in pilot lamp. The pilot lamp
lights up if NEGATIVE SLOPE is selected.
The adjusting speed increases after turning continuously in one
direction. After stopping, starting in the reverse direction resumes
with a slow adjusting speed.
Continuously-variable control to determine the LEVEL of the trigger
point on the trigger signal at which the signal acquisition starts.
if pushbutton DELAY is pushed, the TRIGGER DELAY menu is
displayed. See 4.2.7.1.
If pushbutton COUPLING is pushed, the TRIGGER COUPLING menu
is displayed.-See 4.2.7.2.
li pushbutton SOURCE is pushed, the TRIGGER SOURCE menu is
displayed. See 4.2.7.3.