Alesis AI-1 Reference Manual page 16

BRC. This is required so that the BRC can synchronize to an
AES/EBU or S/PDIF source. Both these connections can be made
while power is on or off, and the ADATs do not need to be turned
on in any particular order (see figure 3).
To connect the AI-1 to a BRC and a multiple ADAT system:
1. Connect one end of a shielded dual male, 9-pin D connector to
the SYNC OUT jack of the last ADAT in the system, and connect
the other end of the cable to the SYNC IN jack of the AI-1;
2. Connect one end of a BNC connector to the 48kHz OUT jack on
the AI-1, and connect the other end of the cable to the 48kHz IN
jack on the BRC;
3. Connect one end of a shielded fiber optic cable into the optic
DIGITAL OUT of the last ADAT in the system, and connect the
other end of the fiber optic cable to the AI-1's "ADAT" optic
DIGITAL IN;
Note: If the other end of a fiber optic cable is disconnected and a
signal is being sent through the cable, you will be able to see a
red light at the output. This is an LED and not a laser light, so
you don't have to worry about damage to your eyes.
4. Connect one end of a fiber optic cable to the AI-1's "ADAT"
optic DIGITAL OUT, and the other end to the optic DIGITAL IN
of the first ADAT in the system.
This last step creates a loop in the digital bus, and thus allows for
communication between all ADATs and the AI-1.
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