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Interfacing
A
BTSC
Stereo
Generator:
The
Orban
Model
8182A/SG
Stereo
Generator is interfaced to the 8182A by means of the 14- pin connector located on
the rear panel of the 8182A. The Card # 7 Output Format jumpers should be in the
"Sum
Out"/"Difference
Out"
positions,
and
the
Card # 7 Output
Preemphasis
Jumpers
should
be
in
the " Deemphasis
Out"
position.
Full
instructions
for
interfacing
the
8182A
to
the
8182A/SG
are
found
in
the
81132A/SG
Operating
Manual.
To
interface another manufacturer's generator to the 8182A, connect the 8182A's
main chassis output to the audio input of the stereo generator. ( See Main Chassis
Output Connections immediately above.)
The
Card # 7 Output
Format
Jumpers
should
be
strapped
in
L/R
or
L+R/L-R
format depending on the requirements of the external stereo generator.
Remote Gain Reduction Meter: A negative DC voltage approximately proportional
to the Total
Master
Gain Reduction
is available between
the OPTIlv10D-TV
rear-
panel
G/R terminal and circuit ground. The voltage scale is approximately - 0.33V
per
dB
of gain reduction, and the source impedance is 8.87K. A standard 0-25dB
Orban gain reduction meter can be connected directly between this terminal (-) and
ground (+).
The Orban
meter has a sensitivity of lmA f.s. and a DC resistance of about 950
ohms.
Full-scale
corresponds
to
30dB
G/R.
Because
only
25dB
G/R
can
be
achieved, the last 5dB of the scale is colored red. ( The purpose of this is to match
the scale to that of the BASS G/R meter, which is capable of, and fully calibrated
to, 30dB G/R.)
If an external meter with different characteristics is used, it is easy to calculate
the
required
additional
multiplier
resistor
for
a 0-30dB
scale
by
the
formula:
M=(9.75/F)-(8870+R), where
M is the required multiplier resistor in ohms,
F is the full scale meter sensitivity in amps, and
R is the internal DC resistance of the meter in ohms.
If
M
is
negative, the meter you wish to use is not sensitive enough, or has too
high an internal resistance.
If
you wish to interface the G/R output to a remote control for telemetry, bear
in
mind
that the input
impedance of the remote control will load down the G/R
output and reduce the voltage according to the gain factor: G=X/(X+8870), where X
is the input resistance of the remote control
in ohms. The scaling of the remote
control should therefore be - 0.33xG volts per dB gain reduction.
3-8
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