M-AUDIO CO3 - Manual (Page 7)

7
S/PDIF streams for you.
Input Source Modes
Depending on the type of input selected, the CO3 functions will differ
according to what conversions can be done, and which cannot. The SCMS
mode settings behave the same way for both TOSlink (Optical S/PDIF) and
S/PDIF (Coaxial) source signals, and whichever is chosen as the source, that
signal is output to both the optical and coaxial S/PDIF output jacks. The
AES/EBU signals require special handling since they don’t carry SCMS
information – more specific information is available below.
Coaxial or TOSlink (optical) S/PDIF Input Modes
When the source is set to coaxial (RCA-type jack) or optical (TOSlink jack)
S/PDIF, "Pass-Thru" becomes the default SCMS mode. Since an S/PDIF
input signal carries SCMS information, all four SCMS modes are available.
When SCMS Pass-Thru mode is selected, the data bits coming into the CO3
S/PDIF inputs are directly copied to the S/PDIF RCA and TOSlink output
jacks unaltered, and the CO3 does a true conversion to the AES/EBU format
(minus the SCMS bits of course). This is the only setting in which true
S/PDIF to AES/EBU conversion takes place – Source set to either S/PDIF
input, and SCMS set to Pass-Thru.
When SCMS modes other than Pass-Thru are used, the associated SCMS
LED will blink. This indicates that the unit is in a SCMS stripping mode and
therefore the AES/EBU output is invalid; only the coaxial and optical
S/PDIF outputs are valid.
AES/EBU Input Mode
When the source is set to AES/EBU, "None" becomes the default SCMS
mode. Since an AES/EBU input signal carries no SCMS information, only
three of the four SCMS modes are available. SCMS Pass-Thru mode
becomes nonsensical because the AES/EBU source has no SCMS data to pass
through. Therefore, Pass-Thru mode is not available from the front panel
when AES/EBU is selected as the source.
In all three SCMS modes, the data bits coming into the CO3 AES/EBU input
are directly copied to the AES/EBU output jack unaltered, and the CO3 does
a true conversion to the two S/PDIF format output jacks. Because there is
no SCMS data in the incoming stream, the CO3 places SCMS data in the
S/PDIF output streams according to the SCMS setting on the front panel.