Lexicon 12T User Manual page 110

S/PDIF Digital I/O
To lock S/PDIF streams to proper clock, you must select S/PDIF 12T as your Audio
Clock Source. If left set to Internal, you will still hear audio, but as the S/PDIF stream
has no clock source to reference you will get periodic ticks in your audio due to sample
slip.
ADAT Digital I/O
To lock ADAT to proper clock, you must select ADATDATA 12T as your Audio Clock
Source. If left set to Internal, you will still hear audio, but as the ADAT stream has no
clock source to reference, you will get periodic ticks in your audio due to sample slip.
NOTE: ADATSYNC 12T selection is reserved for expanded features in an upcoming
software release.
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