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User Manual
Rev. 1.2- 24/01/11
PTX-DDS
7.7 I.T.U.
The I.T.U. function is active only when the internal coder works, it has been
implemented to monitor the output of complete MPX process. When you enable
this function, the AGC is automatically switched off and the CLIPPER R & L function
is added.
The I.T.U. function does not gain on input signal, but it is able to attenuate the
input level until to 20dB.
In the intervention are incleded all the components present in the output like AUDIO,
CARRIER, RDS and SCA. The corrective action is only on audio inputs, then the
contribution of RDS and SCA will be offset by lowering the audio input.
You can change the ITU control reference respect to 0 of legislation in steps of
0.1dBr in the interval between 0dBr and 6dBr, this to adapt the legislation present
in the different countries.
7.8 A.G.C. and Clipper
7.8.1 A.G.C. function for Analogic and Digital audio channel
The A.G.C. function (
Automatic Gain Control
) control in feedback the input level
at the end of audio processing (Low Pass, Preemphasis, etc..) and needs to keep
the audio signal at 0dBu level, avoiding to have signals continuously low or that
continuously takes up the CLIPPER. The control is set with an absolute level (i.e.:
4dB), which indicates how many it can gain or attenuate this check.
The value range is adjustable from 0dB to 12dB, obviously the value of 0dB exclude
the control while using 12dB completely uses completely the control.
The A.G.C. can be activated in 3 modes (Slow, Medium, Fast) and represents
the speed at which very high signals are attenuated or very low audio signal are
gained.
The contents of audio signal is not altered by this control, but it is only altered in
amplitude.
This control works properly when accompanied by CLIPPER-ON function, which
blocks the signal waiting of A.G.C. application.
