Relays are used to control the flow of electricity in a circuit. When given a signal they will either open or close, depending on the internal configuration. The point at which a relay changes it's state is different depending on which state the relay is currently in. A relay that has tripped on at 100% won't go off until the signal drops below 30%, while a relay that is off at 0% won't trip on until the signal reaches 70%. This allows for rough controlling of power setups based on raw voltage signals. Each type of cable has it's own relay, with the relays having the same voltage and current limits as their respective cables.