Tektronix 545A Instruction Manual page 16

Operating
Instructions
—
Type
545A
Fig.
2-6.
The
triggering signal
is
selected
from
three possible sources with the
TRIGGER SLOPE
control.
and
amplitudes without
adjusting
any
of the triggering
con-
trols. In
the
absence
of a triggering
signal,
the
sweep
continues to run to
provide a convenient reference
trace
on
the oscilloscope screen.
The
AUTOMATIC
triggering
mode
is
selected
by
placing
the
TRIGGERING
MODE
switch
in
the
AUTO,
position.
The
triggering source
and
slope
is
then selected
and
the input
signal
is
applied
to
the oscilloscope.
No
other control
adjustments are
required. Since the
TRIGGERING
LEVEL
control
has no
effect
on the display
when
AUTOMATIC
trig-
gering
is
used,
it is
impossible to
select
the point
on
the
triggering
waveform where
the
sweep
is
triggered.
Each
sweep
is
instead triggered at the
average
voltage point of
the
waveform.
DC
Triggering
Mode
The
DC
triggering
mode
is
selected
by
placing the
TRIG-
GERING
MODE
switch
in
the
DC
position. This
mode
per-
mits excellent triggering
on
all
types
of
waveforms
in
the
2-6