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OsciUator Output Voltage
db
0
-1
-2
-3
-4
-5
-6
-7
-
8
-9
-10
-11
-12
-13
-14
-15
I
~~
1/
/
J
J
I
I
I
I
IJ
-16
1
6 8 10
20
40
60 80100
200
500
'KXXl
o/s
Frequency--:;;;,
Fig. 3.
Typical frequency characteristic of the high pass filter in the
Oscillator
output circuit.
The screwdriver
operated
control
is used for
coarse adjustment,
while the
knob
control
allows the
fine
adjustment of the
scale.
"Output Switch"
allows selection
of
output
facilities. With the
switch
in
position "Ext. Osc." the terminal marked
"Oscillator"
at the top of the
instrument front panel is disconnected from the built-in oscillator, and
allows the
output stage of
the
Automatic Vibration Exciter
Control to be
fed from
an
external
oscillator
(or
tape recorder). The frequency
charac-
teristic of the output
cathode
follower is linear
to
within 1 db in the range
o.5
-
20ooo
cps,
and the attenuation
at 500 cps
is o.5 db
approx.
The
output voltage can
be read off the instrument meter when the
"Met~r
Switch"
is in position
"Output
Voltage".
If
the
switch
is set to position
"Linear"
the output stage has a linear
frequency
characteristic
and is
connected
to the built-in oscillator.
In position
"High
Pass" the output
stage
is
connected
to the built-in
oscillator,
the frequency
characteristic
of the
stage,
however,
being changed
according
to the
curve shown
in Fig.
3.
"Output Voltage" potentiometer
controls
the maximum
available
output
voltage. The actual output voltage can
be read on the instrument meter
when the
"Meter Switch"
is in position
"Output
Voltage". During tests
where the
vibration
level is
controlled
by means of the
compressor
circuit
the
"Output
Voltage"
should
be
set
to a position which
ensures
that the
"Oscillator
Voltage"
never
exceeds
10 V.
("
Meter
Switch"
in position
"Oscillator Voltage" ).
10
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