These devices are used to protect electrical systems by redirecting excessive voltage surges to the ground.

Lightning arrestors and surge protectors are designed to protect electronic equipment by absorbing electrical surges. However, these devices are not a substitute for good grounding. They function only in conjunction with effective grounding. The grounding system is an important part of your wiring infrastructure.

Lightning arresters are used to protect electric fences. They consist of a spark gap and sometimes a series inductor. Such type of equipment is also used for protecting transmitters feeding a mast radiator. For such devices the series inductance has usually just one winding.