12V EMP Defender for Vehicles

Helps protect from EMP bursts

This device is rated to protect against EMP, ESD, and CME damage. The EMP Defender works like a flood control gate on a lake. On a lake once the water level reaches a maximum level the extra water is diverted and the lake level is maintained at a safe level. The EMP Defender works like this by shunting the extra voltage away from your electrical circuit allowing it to operate as normal.

Washington State Department of Health Fact Sheet, EMP

More info: https://en.wikipedia.org/wiki/Electromagnetic_pulse