Hi band
It controls the level of high frequencies added to the original audio
coming from the telephone line. With the fader closed the high
processing deactivates.
The action of this control is much more critical that the Low Band,
since an excess of highs processing will generate an “artificial”
sound; and in extreme case “crashed high” sound can take place,
that will be annoying to the listener.
On the other hand, consider that an A.M. radio can require more
emphasis in high frequency than a FM; to obtain a well-known
improvement on the air; therefore the control Hi Band has an ample
rank of action.
The reconstruction level -or amount of highs added to the signal-
depends on the quality of the transmission. This stage will be
affected, mainly, if the line has much background noise.
REMEMBER
The optimal level of work is obtained when the indicator VU
meter reaches the red zone. Lower audio levels can affect
the behavior of the VQR processing.
NOISE Control (expander)
This control is used to reduce the background noise present in the
phone line. It acts only during the silences in the conversation,
attenuating the level of the signal to suppress the noise. This is
quick action gate reason why its effect is imperceptible with normal
levels of noise, not affecting the word.
The NOISE fader acts changing the threshold of the expander/gate.
When background noise is under this threshold the expander/gate
works attenuating the noise.
Closing the fader the expander/gate is turned off. When opening the
fader increases the threshold, that is to say, the signal level below
which the expander/gate goes off. The action of the expander/gate
is showed in the display by the NOISE CONTROL indicator.
Page 28
Telephonic Hybrids
SOLIDYNE
