Alesis BRC Reference Manual page 71

4. Press the DIGITAL I/O button again while the digital input display
reads "AES/EBU" or "S/PDIF";
The display will show the following:
Select tracks to
output to AI-1
All the record and input track LEDs no longer reflect the
record/monitor status. The TRACK INPUT LEDs will now reflect the
current source tracks to be output to the AI-1.
5. Use the TRACK SELECT buttons to select the source tracks;
• To select a single source track, press the desired RECORD-ENABLE
button. The track will now be enabled and its green LED will be lit.
Pressing the same button again will disable that track and turn off
the LED. You may now select a different track.
• A maximum of two tracks may be selected at a time, and they
must come from the same tape machine.
• When a track is selected as a source, any tracks from other
machines that were previously selected will become disabled. If
no tracks are selected, the AI-1's digital output will be silent. If
only one track is selected, it will be routed to the left output of the
AI-1, and the right output will be silent.
The digital output routed to the AI-1 will always be active, whether
DIGITAL I/O is turned on or off. However, if DIGITAL I/O is on and
"ADAT" has been selected as the digital input, the tracks selected for
output to the AI-1 must be the same or higher than the highest
numbered track selected as source or record enabled. For example, if
you have four ADATs (32 tracks) and you wish to output tracks 31
and 32 to the AI-1, it is still possible to simultaneously bounce digital
audio between tracks 1 and 30. In addition, if recording from
AES/EBU or S/PDIF, the tracks selected for output to the AI-1 must be
the same or higher than the highest track that is record enabled.
The reason for these restrictions has to do with the fact that there is a
single 8-channel digital audio bus. The digital connections of the
slave units are serial (i.e. the units are chained together with unit #1's
digital output connected to unit #2's digital input, unit #2's digital
output connected to unit #3's digital input, and so on), there can only
be one set of information (one tape machine) on the digital bus at one
time. This is why the output tracks must come from a unit that is the
same or following the unit in the chain that is receiving the digital
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