Telephone RX (DMP128CP and DMP128CPAT only)
Figure 36. Telephone Rx Signal Path
The DMP128 provides a telephone interface with separate input and output signal
processing paths. The telephone input (Rx) is identical to the other input processing paths
except the AEC block is not used. See Telephone Interface on page126 for additional
information.
NOTE: The country code must be entered before connecting the DMP128 to a
phone system.
Line Output Channels
There are eight mono line output channels. Controls and processing
blocks, identical for each output channel, are described in the
following sections.
Post-mixer Trim Control (TRIM)
The post-mixer trim control provides a fader for fine adjustment of
the program material prior to the output signal chain. The trim control
has a range of – 12dB to +12dB in 0.1dB increments.
Default is unmuted at unity (0.0dB) gain.
Loudness (LOUD)
The loudness processor block, when inserted, applies
a filter compensation curve to the signal in an inverse
relationship to the output volume control setting; the
higher the output volume setting, the less compensation
is applied (see Calibrating Loudness on the next page).
The loudness processor compensates for changes in human perception to varying volume
levels by applying a filter compensation curve to the signal in an inverse relationship to
the gain control setting. The higher the gain setting, the less loudness compensation is
applied. Generally, as volume is lowered, perception of certain frequencies is progressively
diminished, returning to a more flat response as volume is increased. Loudness will boost
those diminished frequencies to the highest degree at low volume levels, decreasing the
boost as volume increases.
Bypass must be disengaged for the loudness processor to function. The bypass button
is red when engaged (loudness control defeated), and gray when disengaged (loudness
control active).
DMP128 • Software Control 58
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