1) The DIN310 and DIN310E are earth leakage relays that use a zero phase current transformer to sense leakage currents and protect circuits. 2) The DIN310E has additional features like a pre-fault alarm contact and positive safety contact. The pre-fault alarm is energized when leakage exceeds 50% of the sensitivity setting. 3) The relays have indicators to display status like tripped, time delay countdown, and settings. Buttons are used to reset trips, test operation, and scroll through settings and fault records.