The 2L11 relay uses double wound relays suitable for connection across a battery with the coils in series opposition, the centre tap being connected to earth.
For a battery without an earth fault the relay remains inoperative due to the opposing coils.
In the event of an battery earth fault the centre earth connection shorts one coil & produces full voltage on the other thus operating the relay.
The relays are rated to withstand an earth fault continuously.
The 2L11 relay is comprised of two relay elements, one operates on positive earth faults & the other on negative earth faults.