The 2L10 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 2L10 relays are single element relays which operate on earth faults of either polarity.
Refer to the 2L11 product page when the battery earth scheme is required to differentiate between positive and negative battery earth faults.