AEQ DIGITAL COMMENTARY UNIT Customer's Manual page 97

The transfer function without DLP would be x=y which corresponds to the 45º
line shown in the graph. The practical result in this situation is that there would
be no modification in the dynamic range.
The system will not allow any dynamic modification at less than -61dB below
saturation level. Therefore with a total range of 80dB, a 1:1 enforced linear
zone is obtained.
If the broadcaster requires a linear response zone ± 4dB around his 0dB
reference level, he can create a further linear response zone between -26dB
and -18dB.
A broadcaster may also require compression zones above and below his
reference level, e.g. that signals ± 4dB from his reference level are compressed
by a ratio of 2:1. In the graphic example shown, it is supposed that this
compression is required between 4dB and 14dB below, and between 4dB and
10dB above his reference level of -22dB, i.e. -26dB to -36dB and -18dB to -
12dB with reference to a 0dB saturation level.
If no further compression zones are required between Vin=-36 and the
enforced value, Vin=-61dB, then the range -36dB to -61dB will be subject to a
1:1.2 expansion ratio, therefore reducing the input noise level.
Finally a powerful signal level limiter must be included for the limitation of input
signals 10dB above the reference level. A 10:1 limiter is built-in to close the
upper end of the curve for this purpose.
The following section describes the programming of similar custom designed
dynamic curves using the control software.
Digital Commentary System
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