From the Manufacturer
The Canon LC-4 is an extended-range wireless controller system designed for professional and advanced amateur users of EOS cameras with N3 remote control sockets.
Based on the LC-3 wireless controller, the LC-4 offers an enhanced connector on the receiver unit, which has been changed from a threaded to a quick-lock type. The remote controller provides remote shutter release capability with a maximum transmitter to receiver distance of 300 feet.
Models:
EOS 20D, EOS 10D, 1D, D60, D30, D2000, 1v/1v HS, 3.