The I Sync 4 has 4 independent radio channels for use where multiple photographers may be using wireless triggers such as at a wedding etc. Now you can set the channel and still keep on shooting without interference from other photographers. A major benefit of the receivers is the ability to switch between optical triggering or wireless triggering. Optical triggering is similar to a built sync cell on a studio flash heads. Wireless triggering allows out of sight flash triggering or around walls and most obstacles up to a maximum distance of 30 mtrs (100 feet). Each receiver has a built in light stand tread on the bottom to allow your speedlite to be stand mounted. In addition a PC sync cable and socket is included along with a mono jack converter to fit both large and small jack sync sockets for connecting to studio lighting. Runs on long life lithium batteries (included).