are active 1 which causes the and output signal flash_on to go active 1 and enable the flash as a result the flash driver unit 6 switches the flashlight element 2 on and opens the shutter device 11 at instant t 2 the enable signal goes active 1 and turns the transmitter unit 1 on at instant for the first time slot of frame n 1 as a result the inverted enable signal at the second input of the and circuit goes inactive 0 which causes also the and output flash_on to go inactive and the flash power supply is disabled and the shutter 11 is closed although the flash_control signal remains active 1 at the instant t 3 at the end of the first timeslot in the frame n 1 the enable signal goes inactive 0 and the inverted tx enable signal goes active 1 now both inputs to the and circuit 7 are again active 1 which causes the and output flash_on to go active and enable the flash and the shutter 11 as a result the flash driver unit 6 switches the flashlight element 2 on at the instant t 4 the enable signal goes active and turns the transmitter unit 1 on for the first time slot of frame n 2 as a result the inverted enable signal at the second input of the and circuit goes inactive 0 which causes also the and output flash_on to go inactive and the flash power supply is disabled and the shutter 11 is closed although the flash_control signal remains active 1 at the instant t 5 at the end of the first timeslot in the frame n 2 the enable signal goes inactive 0 and the inverted enable signal goes active 1 resulting in enabling.