Specifications

192 Digital I/O Guide16
Synchronization Mode and
Clock Source
The 192 Digital I/O lets you synchronize your
Pro Tools|HD system to most digital clock refer-
ences in use in today's complex, multi-unit pro-
duction environments.
The Hardware Setup dialog lets you specify
among digital input sources and select a Clock
Source.
Choices for Clock Source vary depending on
Sample Rate and Digital Format (AES/EBU,
S/PDIF, or Optical S/PDIF).
Pro Tools|HD and the 192 Digital I/O give you
multiple clock reference choices at all sample
rates and digital format settings.
To choose a clock source:
1 Launch Pro Tools.
2 Choose Setups > Hardware Setup.
3 Select a Digital Format from the enclosure
port choices: AES/EBU, S/PDIF, or Optical
(ADAT). If not using the enclosure ports for
clock, skip this step.
4 Click the Clock Source pop-up menu and se-
lect a synchronization mode. If the desired clock
is not listed, check your Digital Format settings
in both the Main and Digital tabs to be sure you
have enabled the appropriate digital port and
format. Choices for Clock Source also vary de-
pending on Sample Rate.
5 Click OK to close the Hardware Setup dialog
when you have finished.
Your choice depends on which device in your
setup you want to make the master clock device.
192 Digital I/O can only be the clock source
when it is the master audio interface. If you
choose a clock source on another HD I/O other
than the Loop Master, Pro Tools will automati-
cally designate the new interface as the Loop
MASTER peripheral, switch to it for the chosen
Clock Source, and set all other HD I/Os to Loop
Slave mode.
Clock Source and Loop Master
In the Hardware Setup dialog, you can choose a
clock source available from any HD I/O. Choos-
ing to use a Clock Source will, in expanded I/O
systems, automatically make that I/O the Loop
Master. The LOOP MASTER LED will light on
the front of the Loop Master I/O.
Because any HD I/O can be the Loop Master,
you can use any of the digital ports on any HD
I/O as your system clock source.
Digital Format
The Digital Format section enables you to
choose which Enclosure port the 192 Digital I/O
will use for digital audio input. Only one Enclo-
sure digital input port can be used at a time, al-
though the AES/EBU and S/PDIF outputs are mir-
rored at all times.