thanks ken, i wasn't aware of it !
i've found it !
fast mode must be used
always a good idea to read the user guide !
Additional functions
fast mode
The Profoto Air Sync and Profoto Air Remote devices deliver sync signals with a very short delay.
In Fast mode, the delay is even shorter.
Fast mode is only recommended when working with very short camera shutter times, as the battery consumption is considerably higher.
In Fast mode, the remote control functionality (available in Profoto Air Remote) is disabled and inoperative.
Fast mode is used when an extra short sync signal delay is required.
1. To enter Fast mode, press and hold down the Mode Button [4] for 7 seconds,until there is a beep and the Transmit Indicator [3] starts to blink fast.
2. To exit Fast mode, press the Mode Button [4] once.
Silent mode
This section only applies to the Profoto Air Remote device.
1. Ensure that the Profoto Air device is turned off.
2. To enter Silent mode,press and hold down the Head Button 0 [10] and the On Button [5] simultaneously until the Transmit Indicator [3] is illuminated.
3. Silent mode is automatically disabled when the device is turned off.
Disable Auto Power off
1. Ensure that the Profoto Air device is turned off.
2. To disable the Auto Powe rOff function, press and hold down the Mod eButton [4] and the On Button [5] simultaneously. When deactivating the auto power off function, the device confirms this with a short beep immediately.
3. The Auto Power Off function is automatically enabled when the device is turned off.
factory settings
1. Ensure that the Profoto Air device is turned off.
2. To reset the Profoto Air device to factory settings, press and hold down the Test Button [6] and the On Button [5] simultaneously until there are three beeps.