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User Manual
Rev. 1.2 - 24/01/11
PTX-DDS
7.6 Audio Rescuer
7.6.1 Preliminary Considerations
The TRDSP card has available an Optical-AES/EBU digital input, two balanced
analog inputs (audio channel left and right) for stereo broadcast, unbalanced MPX
input scanned up to 100 kHz and 2 SCA adjustable inputs mixed in analogic with
MPX input.
For automatic switching are considered three points:
• Signal level on analog audio input (L.A.). The reference threshold is calculated
independently on left and right input as the value is relative to the input level
set. The threshold refers to reading, so first of all audio processing such as
PB, Preemphasis, Clipper, ITU or A.G.C.. The input signal is considered valid
if both channels are valid. When you set the analogic CODER as MONO_L the
level of the right channel is always considered valid.
• Signal level on digital audio AES/EBU, after conversion, independently the
optical or balanced source (L.D.). The reference threshold is calculated
independently on left and right input as the value is relative to the input level
set. The threshold refers to reading, so first of all audio processing such as
PB, Preemphasis, Clipper, ITU or A.G.C.. The input signal is considered valid
if both channels are valid. When you set the digital CODER as MONO_L the
level of the right channel is always considered valid.
• Signal level on MPX input, which contains the analogic sum of the three MPX,
SCA1 and SCA2 unbalanced inputs. When this input is primary or secondary,
the SCA inputs are automatically blocked to prevent measurements from the
SCA (L.X.). The reference threshold is calculated in relative mode referred to
the setted input level.
• Digital stream. It is found the consistency and validity of the digital texture by
reading the FLAG status of the audio device (T.D.). To establish the validity of
the texture are measured also the break for minute, which must be less than
the parameter set by the user.
• 19KHz Tone. The presence of 19KHz pilot tone is continuously monitored on
MPX input (T.P.). When you set the MPX CODER as MONO, the pilot tone is
excluded from the aid algorithm.
7.6.2 Validity of signal sources
The following table defines the validity of sources in different configurations.
