This unit will automatically flash when any other flash is triggered. Or, it can be used as a master flash with a PC Cord (RS-3154) plugged directly into a camera's PC socket. This unit features a unique adjustable reflector allowing the photographer to control the angle of the light from 310 degree to 180 degree to 45 degree. The photographer can also set the unit to ignore a pre-flash that some cameras' built-in or auxiliary flash units feature. Guide number if 45 @ ISO 100/ft. Fits standard AC sockets for power. Unit can also be triggered via the built-in test button.