Inovonics 235, Инструкция по эксплуатации и техническому обслуживанию

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Section III
SETUP AND OPERATION
OPERATIONAL OVERVIEW AND PANEL APPOINTMENTS
This section leads off with an overview of the 235 Processor with
particular reference to front-panel indicators and controls. All functions
are described and explained in this overview. Whether or not you
believe in reading Manuals, please at least check these descriptions to
verify that our terminology is in agreement with your understanding. If
you call us (especially if you use our toll-free number!) with a question
that is answered here, we are likely to be very cross with you.
AGC 235 processing begins with slow, “gain-riding” Automatic
Gain Control, or AGC. This is not considered a dynamic
processing function because it does not alter program
dynamics and contribute to perceived loudness. The
purpose of the AGC is to erase long-term variations in the
input program level and to present subsequent processing
stages with a consistent program signal.
Input levels can wander up and down for a number of
reasons. Among these are: 1) an operator’s lack of
attention to manual gain-riding, 2) different interpretations
of console level meter readings among board operators, or
3) the misrepresentation of the program signal waveform by
the traditional, sluggish VU meter.
AGC in the 235 Processor is “gated.” It does not “hunt” or
bring up background noise during pauses in the program.
AGC gain freezes when midrange program energy falls
below the preset gating threshold.
AGC response to the program waveform is quasi-peak-
responding. Its 10-millisecond integration is similar to the
response of a European Peak Program Meter. Correction ,
on the other hand, is slow: only 1dB every couple of seconds.
This makes overall operation roughly equivalent to a human
operator watching a PPM and sneaking the level up and
down, slowly and unobtrusively.
AGC correction spans a 20dB range. The
INPUT GAIN
control is adjusted to center AGC action, effectively yielding
a ±10dB correction window. AGC gain is metered by the
associated bargraph display, and the bottom-most GATE
OPEN indicator lights whenever the circuit senses legitimate
program energy to enable circuit operation.