This form of metering is controlled buy a master flash and a series of "slave" flash units.
The master sends a high speed coded signal to all slaves to fire a flash at 1/32 power. The light from the scene travels through the lens and our camera report back as to what it has determined as being the correct exposure.
Photographer can make adjustments to increase or decrease the power output and therefore the amount of light that they desire to achieve the desired exposure.
Tip - Use MAHA Battery charger MH-C801D which charges 8 batteries and use Powerex 2700mha rechargeable batteries for best results for professional photography.