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1.
DESCRIPTION
Channel-selector.
The two-channel-selector consists of a low noise relay driven by the output
of a bi-stable multivibrator. The multivibrator may be blocked in one of the
other positions by setting the CHANNEL SELECTOR switch in "left" or
"right" positions. In the "left-right" position, an automatic switching is
obtained at a recurring frequency of 1.2 Hz. In other words, each channel is
connected during a period of o.4
seconds.
Transients and switching times are
shorter than o.02 seconds.
Equalizing Filter Section.
Fig. 1.10 shows the three different equalization characteristics provided by this
section. They are selected by means of the FILTER SWITCH which also has
a fourth position marked "Direct" where the filter section is short-circuited us
needed when testing sound reproducers other than record players (e.g. tape
recorders) .
The filters are of the RC type and are designed to be used as external filters
on the B
&
K amplifiers such as the Microphone Amplifier Type 2603. The
standard characteristics are obtained only if the test records are rotated at the
specified speed.
Synchro-starter Section.
General Description.
The purpose of this section is to command the paper drive start of the Level
Recorder Type 2305 at the end of the 1 kHz start signals recorded on the test
records, thus automatically ensuring synchronism between the instantaneous
test frequency on the record and the frequency calibration of the recording
paper.
QR 2009
Tested
pick-up
Gear
Level Recorder
Paper drive
1-i_._+WW\Hiiii---1~
(!)
.._____.,
~til
Automatic
113
octave
filter switch
Fig. 1.16. Block diagram of the equipment for automatic frequency response
and separation measurements.
14
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