Yongnuo RF-603 III adopts a global free FSK 2.4GHz wireless channel which can be suitable in many countries. RF-603 III with FSK system, can be more effective to guarantee speed, distance and stability. Within capacious areas, the remote control distance may reach to 100m and suitable for RF-603I. RF-603 II wireless flash trigger kit is formed by two same transceivers. It can be set to single transmit state (TX), which will be more convenient for testing flash and can be set to transceiver state (TRX), automatically switch transmit and receive state, adopts focus and shutter function in "TX" and "TRX" state respectively. Transmitter supports single contact triggering, supports wireless wakening up and triggering the flash through the camera hot shoe, with PC sync cable (optional) can be trigger studio lights, with specially camera shutter connecting cable can realize wired / wireless shutter release remote control, supports controlling multiple cameras and flashes at the same time. The highest flash sync speed up to 1/320 second (some of models may only reach to 1/250s or less, difference combination of models of flash and camera using may achieved difference flash sync speed).