Yongnuo Yn560 IV Master Radio Flash Speedlite + RF-603 II Flash Trigger for Canon Pentax Olympus The YN560 IV can be used as master unit, provides 3 independent groups with controlling ability, realizing remote control the flash mode, flash output and focal length of the YN560 IV and YN560. One YN560 IV can respectively receive the wireless signal from YN560 IV, YN560-TX, RF-603(/),RF-602,with optional 16 channels. The YN560 IV can triggered through the set top of the camera, 2.4G wireless triggering, S1 and S2 pre flash cancel mode. When the sound prompting system is enabled, the different sound ways will prompt different operating state of the flash so as allow you focus on shooting. RF603adopts a global free FSK 2.4GHz wireless channel which can be suitable in many countries.