Tektronix T912 - Page 18

Operating
Instructions—
T91
2
1981
21
Fig.
2-6.
Time
base
front
panel
controls
and
connectors.
MODE—
Selects
the
operating
mode
for
the
trigger
circuit.
AUTO:
With
the
proper
LEVEL
control
setting,
the
sweep
can
be
triggered
by
trigger
signals
with
repetition
rates
above
about
20
Hz.
in
the
absence
of
an
adequate
trigger
signal,
or
when
the
LEVEL
control
is
misadjusted,
the
sweep
free
runs
to
provide
a
reference
display.
LEVEL-
—
Selects
the
amplitude
point
on
the
trigger
iv
signal
at
which
the
sweep
is
triggered.
Usually
adjusted
for
the
desired
display
after
trigger
SOURCE
and
SLOPE
have
been
selected.
^
X
(External
Trigger)-Provides
input
for
external
W trigger
signals
or
for
X axis
signals
in
the
X-Y
mode.
NORM;
Permits
triggering
on
displayed
signal.
In
the
absence
of an
adequate
trigger
signal,
or
when
the
level
control
is
misadjusted,
the
sweep
does
not
run
and no
display
isvisible.
Setting
SOURCEto
LINE
position
provides
an
adequate
trigger
signal.
SINGLE
SWP:
Sweep
runs
once
on
firsttriggered
event
after
RESET
is
pushed.
Another
sweep
cannot
be
triggered
until
RESET
is
pushed
again.
May
be
used
to
store
one
event
or
several
events
in
succes-
sion.
RESET:
Resets
the
sweep
after
a
single
sweep.
Must
be
pushed
after
a
single
sweep
has
occurred
for
another
sweep
to
run.
SLOPE—
Selects
the
positive-
or
negative-going
slope
of
the
trigger
waveform.
+OUT:
The
sweep
can
be
triggered
from
the
positive-going
portion
of
a
trigger
signal.
-IN;
The
sweep
can
be
triggered
from
the
negative-going
portion
of
a
trigger
signal.
SEC/DIV—
Selects
calibrated
sweep
rates
in a
1-2-5
Iv
sequence.
X1-X10
variable
control
must be
in
theXI
detent
position
(fully
ccw)
to
read
calibrated
sweep
rates
directly
from
the
SEC/DIV
knob.
Knob
numerals
with
u
underneath
indicates
sweep
rates
in
•
microseconds/division;
numerals
with
m
under-
neath
indicate
sweep
rates
in
milliseconds/division;
positions
with
no
symbol
under
the
numerals
in-
dicate
sweep
rates
in
seconds/division.
~N
X1-X10—
Provides
calibrated
sweep
rates
when
in
IJ
X1
(fully
ccw)
detent
position.
Increases
the
horizontal
gain
by
a
factor
of 10,
providing
at
least
50
ns/div
sweep
rate
in
the
X10
detent
position
(fully
cw)
with
the
SEC/DIV
knob
set
to .5 fis.
POSITION
—
Controls
the
horizontal
position
of
the
crt
display.
2-6
REV.
A
APR
1977