Specifications

18
e. MULTIPLEX-SINGLE Function
The operation mode of the Model 141 may be selected via the
MULTIPLEX-SINGLE
switch on the front panel. In the
SINGLE
position, the output from either of the three
microphone amplifiers may be selected. This allows the levels to be equalized via the
CHANNEL GAIN
slide potentiometers. The unit may also be used as a line amplifier
for a single remote microphone by simply placing the
MULTIPLEX-SINGLE
switch in
the
SINGLE
position and setting the
MIC. SELECT
switch to the appropriate position.
f. MIC. SELECT Switch
This switch selects between either of the three microphones when the
MULTIPLEX-
SINGLE
switch is in the
SINGLE
position.
g. Output Connector
The output from the Model 141 is taken from a two terminal barrier strip located on the
end of the instrument. Any simple line pair may be used to connect it with the
LINE
INPUT
of the Model 140. The Model 141 has the same gain as the microphone amplifier
in the Model 140 and therefore will yield readings of the same accuracy as a microphone
connected directly to the Model 140's
MICROPHONE
input. It may be necessary to
observe the polarity of the connection to minimize hum pickup.
3. Operation
In practice, three microphones (usually the
"job"
mics) are connected to the Micplexor
down on the floor of the room being equalized. The output of the Model 141 is connected
to the Model 140 via a simple unshielded pair. The Model 140 may be located some
distance away, such as in the control room or at the console. This alleviates the necessity
for long shielded cables. The three microphones are arranged in close proximity to each
other with the
MULTIPLEX-SINGLE
switch in the
SINGLE
position. A pink noise
signal from the Model 140 is fed to the sound system, then the outputs from each of the
three microphones is equalized by adjustment of the three
CHANNEL GAIN
controls on
the front panel. The microphones are then placed across the axis of the room, and the
MULTIPLEX-8INGLE
switch is placed in the
MULTIPLEX
position. A real time
analysis of a spatial average of the sound field is then displayed on the Model 140.