This unit is triggered by light duty power such as a switch on the dash and/or pressure switch and in turn closes heavy contacts and then allows heavy power at 100 amps to pass through.
To give you an idea of how much 100 amps is, a 65 watt head light is only 5 amps and so it can handle 20 headlights.
Ideally these are used for passing power to heavy duty 12V air compressors such as the big BOSS compressor.
