About the product RF-603 II, the manual Flash trigger and shutter release ( you can use those two functions simultaneity ), it adopts a global free FSK 2.4GHz wireless channel which can be suitable in many countries. RF-603 II 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 is suitable for the first generation RF-603. Improved Features: 1. Higher sync speed than the first generation --- The highest flash sync speed up to 1320 second (some of models may only reach to 1250s or less, difference combination of models of flash and camera using may achieved difference flash sync speed). 2. Adding the Locking rings 3. Improved Flash Shutter control Buttons 4. Working for more non CanonNikon cameras and single firing pin cameras --- ALL Standard Hot shoe DSLR Camera except Sony and Minolta. Note: We suggest Canon cameras users choose RF-603 II Canon version, Nikon Camera users choose RF-603 II Nikon version, other cameras users can choose any version. 5. Adding the power switch for single transmitter --- Set the power switch on TX (single transmit) or TRX (transmit-receive automatic switch) state according to different shooting requirement. When it used as wireless triggering transmitter and flash testing, set to "TX"; When it used as wireless triggering receiver, using shutter release or other extended functions, set to "TRX". set to OFF means turn off the power. 6. Suit for first generation, you can use them together. C1 Version: ---Canon 1100D 1000D 700D 650D 600D 550D 500D 450D 400D 350D 300D 60D ---Pentax K20D K200D K10D K100D ---Samsung GX-20 GX-10