This Dot-Line RS-RT04/C3 RF Remote Release is a wireless radio remote that works with Canon EOS 5D, 10D, 20D, 30D and 40D digital cameras. It consists of two parts: a receiver/trigger that connects to the camera's cable release socket, and a separate sender. The remote can have a range of up to 100' under optimal conditions, and it features a two-position switch, for focusing operation or shutter release.
Note! The receiver takes 2 "AAA" batteries (not included)