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MECHANICAL ZERO
ADJUSTMENT:
DIRECT INPUT:
PREAMP. INPUT:
Enables meter to be zeroed (using a screwdriver) when power is not ap-
plied to the instrument.
Coaxial socket input to the input amplifier. Input impedance,
1
MO 1180 pF. The socket accepts the standard B &
K
coaxial plug JP
0101.
7 pin socket for connection of B & K microphones via their preamplifi-
ers. The socket provides the necessary voltage supplies for the pream-
plifiers and a 200 V polarization voltage for condenser microphones. In-
put impedance 900 kO 1180 pF. The socket accepts the standard B & K
7 pin plug JP 0701. The pin connections of the socket are shown in
Fig.2.2.
Heating element
Supply
Signal
Ground
171410
Fig.2.2.
Connections to PREAMP. INPUT socket
SENS.:
INPUT:
CALIBRATION:
GAIN CONTROL:
UNCAL.:
INPUT SECTION ATIENUATOR:
14
A screwdriver operated potentiometer situated at the side of each in-
put. It adjusts the gain of the input amplifier in order to compensate
for different transducer sensitivities. The two adjusters work independ-
ently of each other and each has a range of about
1 0
dB.
Two push buttons
.
"Direct" input or input via an external "Preampli-
fier" may be chosen by depressing the appropriate push button.
Four push buttons:
"Ref. 50 mV". Supplies the 50 mV RMS 1 kHz sine-wave signal for in-
terna I ca I ibration purposes.
"Insert Volt. Cal.". Choice of internal or external signal. The "Exter-
nal" is for use when an external frequency generator is used, see sec-
tion 3.2.4.
"Cal. Off". For reset of the other CALIBRATION buttons to a passive
position.
For continuous control of the gain of the first amplifier. When in posi-
tion "Cal" the gain is fixed. Maximum attenuation approx. 1 0 dB.
This light is lit when the GAIN CONTROL knob is not in the "Cali-
brated" position.
For attenuation of the input signal in 1 0 dB steps. Voltages marked
around the knob show the maximum RMS input voltage (for full scale
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