Test (Using Canon system)

Di866 on camera, in Wireless mode, Master, Channel 1,
Group A, TTL
M set to 'NA''

Di622 Mark II, set to wireless TTL salve mode, Channel 1, Group A by default.

Di866 will trigger a flicker of flash for the IR/TTL signals to reach the slave flash etc. This 'TTL pre-flash' wlill not affect the overall exposure of the image.