The Einstein Receiver allows remote triggering and remote power control of the Einstein E640 light. Simply attach the Einstein Receiver to the port on the top of the E640 light and you're all set. The Einstein Receiver is powered directly from the E640 and is configured using the display on the E640. The Einstein Receiver requires no batteries. It provides stop accurate power control of the E640 light throughout its entire power range and may be assigned to one of 4 groups/zones.