Solidyne HL 202, Руководство пользователя

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3.1.1 Return to phone line
Most of the existing telephone hybrids on the market today, were
designed over 30 years ago for analogue telephone exchanges
(PBX) Solidyne hybrids, however, have been recently designed for
private or public telephone exchanges today, which are fully digital.
The new technology Hybrids are recognized because they have no
control of air return level to phone line. This is because inside the
hybrid Solidyne uses an audio processor for return signal that
includes AGC, peak limiter & audio signal filtering. Therefore the
return is automatically adjusted during the transmission and its level
is the maximum allowed by the modern digital telephone
exchanges.
If you want to check the return level to phone line, you must use a
oscilloscope to be placed in parallel with the telephone line and
must verify that the signal is 2 volts peak to peak.
Please note that above this level the return can produce problems
that will cause intermodulation distortion in the audio signal that
goes to air. So in Solidyne hybrids we use a processed return
channel, to avoid distortion at the on-air signal. There are hybrids
manufacturers that maintain the return control level as they did in
the past. This allow operators to adjust "by hunch" this critic level.
This makes the voices of the reporters and interviewed people
distorted or with coloration.
In Solidyne obviously, we keep a high grade of excellence in the
audio quality of the hybrid on-air sound. And that quality do not
depend on the operator settings. Note that the Solidyne Hybrid on-
air audio quality of the local journalists is ever perfect and without
any coloration.
To achieve this level of quality that other brands do not offer, we use
a narrow-band return filter. Then the return signal is limited to the
band 400 – 2.200 Hz in order not to distort the signal to the air. This
narrow band intelligibility remains high (due to processing) but
occasionally may seem to the remote people that it "has little
volume" because his band is narrow. This should not worry because
it is a subjective sensation that does not affect the intelligibility of
speech.
Page 22 Telephonic Hybrids SOLIDYNE