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3-2
OPERATION
Orban Model
464A
Co-Operator
Controls
and
Meters
A
pop-off
cover
protects the following three pairs
of
set-up
controls:
METER
CALibration
controls
calibrate
the
peak
output
level meters so
that
full-scale
indicates
a
peak anywhere between -2 and
+20dBu
(OdBu = 0.775V
RMS).
With these
controls,
the
meters can be
precisely
matched
to
the
overload
or
100%
modulation
point of
equipment
being
driven
by
the
Co-Operator.
HF
LIMITing
PRE-EMPHASIS
switches
determine
the
pre-emphasis curves
for
the high-frequency
limiter.
The
25ns
setting
produces
the
least
high-frequency
limiting:
the
150ns
setting
produces
the most.
If
the
internal
pre-emphasis jumper
is in
the
pre-emphasized
output
position,
the switch also
determines
the
pre-emphasis
at
the
Co-Operator's
output.
OUTPUT
ATTENuator
controls
adjust the gain
of
the
balanced
line
amplifiers
for
matching
output
levels
to
equipment
that
does
not
have
convenient
input
sensitivity
controls.
GAIN
REDUCTION
meters show
the true
peak
gain reduction
in
dB.
If
the red
LED
at
the
far right of
the
bargraph
lights,
no
further
gain reduction
is
available.
HF
LIMITing
Indicators
light
when
HF
limiting
occurs.
PEAK OUTPUT
LEVEL
meters
indicate
the
peak
output
level of
the
Co-Operator
just
before
its
final
"active
transformer"
line
amplifier.
The
meter reads
within
0.5dB
of
the
true
peak
value
of
a 10-microsecond
pulse.
The
meter
is
particularly
useful
as a
peak
modulation
indicator
for
a
microwave
STL
or
FM
subcarrier
generator
that
does
not
have
accurately
calibrated
peak-reading meters.
INPUT ATTENuator
controls
determine
the
amount
of
gain reduction
by
adjusting
the
drive
level into
the
leveler
and
compressor.
GATE
THRESHold
indicators
light
when
the
input levels
fall
below
those
set
by
the
gate
threshoW
controls.
GATE
THRESHold
controls
determine
the input
level
below which
the
leveling
gain
control
is
"frozen"
to
prevent noise rush-up during
pauses and
low-level
program
material.
Once
frozen, the leveling
starts
drifting
slowly
toward a
point
equal
to
the
average
gain reduction
over
the past
30
seconds.
The
fast
compression
release
process
is
unaffected.
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