The Dogtra Surge Protector for the EF-3000, EF-3000 Gold, and EF-3500 systems are specifically designed to protect electronic pet containment system transmitters against damage from lightning. It contains two protectors one to stop lightning currents from coming in on the loop wire and the other to stop lightning currents from coming in on the AC power connection. It can be used w/ all electronic pet containment systems, w/ protection for AC & loop with a larger capacity to dissipate surges and increased surge current ratings. It is easier to attach the loop wires to the unit which allows you to have better loop connectors and reduced risk of a system failure. It has a power indicator that comes with a space-saving design.