Trigmaster Plus II is a transmitter and receiver system built into one pocket-sized unit. It uses a common 2.4G signal to trigger strobes, Speedlight"s and cameras. It also has zone control, relay mode, a max flash sync speed of 1/320s, a range of 500 meters, 6 channels, and more. Whatever your triggering needs, you can easily master them with Trigmaster Plus II. Extremely reliable, with a strong 2.4G wireless radio signal. Trigger your flash indoors or outdoors, without suffering from interference or misfires. Relay Mode enables long distance control - fire your flash or camera up to 500 meters away. A 3rd unit relays the signal for further reach. Commonly used for shooting remotely, on safari, sporting events, etc. Can also utilize zones, and can trigger multiple cameras or flashes, not just one. Remotely trigger your camera AND flash at the same time with a trigger in your hand, while enjoying complete freedom of movement. It"s useful for a range of applications, from remote portraiture, engaging with your subject away from the camera, etc. Power Indicator displays power in 6 levels, and blinks red to indicate low battery power. It"s designed for a long shooting life, so you don"t have to worry about battery power. With 2 AA batteries, normal standby power is 200 hours, and 80 hours while in use. Trigmaster Plus II is compatible with all previous 2.4G triggers in the Aputure family. So if you"ve got others in your arsenal, don"t worry, they will work together.