How the "ELCB & SOCKET TESTER" Work

I "liberated" the italicised text below, from another site, rather than typing it out laboriously:

The earth leakage circuit breaker (trip) compares the current flowing in the live and neutral lines. If there is any difference it means that difference in current is flowing along the earth line or through a different path to earth (maybe plumbing pipes etc). It is designed to trip when this difference exceed a certain amperage of current flow. It is not designed to protect against a short circuit but only when current does not return via the neutral line.

So what the "Test" button does, is switch a high resistance resistor temporarily between the live wire and the earth pin inside the tester.

The ELCB detects the imbalance between the voltage/current supplied via the live wire, and that returned via the neutral wire, and operates a small solenoid interlock, releasing a mechanical latch, and the ELCB fully releases due to a spring which open-circuits it, switching the power off rapidly.

The imbalance voltage/current flows through the earth conductor, to the ground connection....