This device is great for allowing power to pass through based on a switch or ignition circuit for users of our GPS Tracker for Custom Applications who mount it to a trailer.
However it can help anyone with a trailer.
For instance, normally an accessory (like a GPS tracker or lights) can drain the tow vehicle battery if the trailer is still hooked up.
An easy solution is to always remember to unplug your trailer if the tow vehicle is off, and always remember to plug it back in before you set off again.
But we all forget.
The smart solution (and you are smart) is to allow power to a trailer only when you want it to, like when the tow vehicle is running, and you do that with one of these.
Power from battery into one pole and power out of the other pole to the trailer plug (or anything else), with the smaller third pole connected to an ignition circuit. That is, when the ignition is on, it activates the solenoid to allow power to pass.