Rollei Pro Transmitter Mark II Instructions Manual page 35

Functions
9. SYNC-X
Set this function to "ON" (On) to maximize the speed of the flash for
taking continuous pictures with the camera .
10. Background lighting
With the "Back light" setting, you can set the background exposure to
dark (MIN), medium (MID) or light (MAX) .
11. Speed "Nor"/"Boost"
The newer firmwares of the Pro Transmitter Mark II can set "Wireless
Speed" between "NOR" and "BOOST" . Note: Our Rollei Flashes can only
be operated with the „NOR" setting via radio transmitter!
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