When first shipped with Pro Tools 5.3, Sync I/O does not support Loop Clock. To use SYNC I/O as the clock master with a 92 I/O or 192 I/O interface, connect the external clock 1x/256x out of the SYNC I/O to the corresponding in of the first audio interface. Sync mode for that interface (and all others in the chain) should then read "EXT" when Pro Tools is launched.SYNC I/O will support Loop Clock in a subsequent release of Pro Tools and SYNC I/O firmware.