"40A" designation indicates the maximum rated current of the circuit breaker, which in this case is 40 amperes.
"4P" designation signifies that the ELCB has four poles. In electrical terminology, a pole refers to a set of contacts that opens or closes the circuit.
"300mA" indicates the sensitivity of the ELCB, measured in milliamperes. This value represents the minimum level of earth leakage current that will cause the circuit breaker to trip and disconnect the circuit.
primary function of the ELCB is to protect against electrical shock by detecting stray currents that flow from the live conductors to the ground (earth).
ABB FH204-404300 likely features a mechanical tripping mechanism that activates when the leakage current exceeds the predetermined threshold