Specifications

14
A plastic sheet with a display grid printed on it is furnished with the instrument. This fits
in front of the
LED
display. By using a soft wax pencil (such as a china marking pencil)
date may be quickly copied off, and then transferred to a permanent record at leisure.
Further, desired response curve shapes may be drawn on the plastic sheet for use as an
overlay during adjustment of a filter set to a desired response. After the uncorrected
house curve has been displayed and examined, then judgements are made on the filter
corrections to be applied to arrive at the desired house curve. A booklet on equalization is
available upon request to White Instruments.
An alternate procedure is to use the microphone multiplexor furnished as an accessory to
the Model 140. This battery-operated device accepts the inputs of up to 3 dynamic
microphones, and sequentially switches their inputs at a slow rate to minimize spectrum
distortion. The output from the
"Micplexor"
is at a high level and may be carried to the
Model 140 location through any wire pair. The output is at line level and should be
plugged into the
"Line"
jack. Further procedures are as described.
7. Adjustment of Masking Noise Systems
In open plan office noise masking systems, the noise is of course supplied by an installed
noise generator and speaker array. The objective will be to adjust the equalizer filters
supplied with the masking system so that a specified curve is obtained. It will be helpful
to sketch this curve in advance on the plastic overlay, using suitable jumps in the plotting
to cover the considerable dB range that must be analyzed. With this overlay, and
manipulation of the
dB-SPL
control, the full curve may be observed as the equalizer
filters are adjusted to the specified curve.
8. Rear Panel connections
On the rear of the Model 140 a seven terminal barrier strip is mounted. Certain functions
are available there which will be useful for rack mounting or the remote display of the
analyzed signal.
a. LINE AMP IN
The
LINE AMP
input is brought to the rear panel to facilitate connection while the unit
is rack mounted. This input is the same as the
LINE INPUT
on the front of the Model
140. The shorting strap to the
PRE-AMP OUT
terminal must be removed when a signal
is fed to the Model 140 via this terminal.
b. PRE-AMP OUT
This connection is the output of the
PRE-AMP.
The signal that appears here is the signal
into the
MICROPHONE
input on the front panel plus 60dB.
NOTE:
The
LINE AMP
and
PRE-AMP
terminals must be shorted together for normal operation of the Model
140. The
LINE
input and the
PRE-AMP
output are made available for the future
insertion of weighting networks, should the occasion arise. Please consult the factory
before attempting this function.