Gelco high sensitive current operated earth leakage circuit breakers [elcb + mcb] are designed to give total protection by disconnecting the supply against risk of dangerous and possibly lethal electric shocks. It detects dangerous leakage current exceeding the generally accepted safe limit of 30 ma and isolates the affected section of installation. It conforms to bs 4293:1983 and is 12640: 1980. A core balance transformer senses the sum of all-current to be normally zero. Any leakage to earth is sensed as an unbalance creates small signal in secondary winding, which is fed to a highly sensitive electronic circuit to trip the mcb. It also protects against overload and short circuit. It is available in single phase as well as in three phase up to 63 a. Leakage current setting is adjustable from 10 ma to 30 ma and from 30 ma to 100 ma. It is with building low/high voltage cut-off [low cut-off-below 130 v and high cut-of: above 208 v optional]. Led indication for working condition and emergency by-pass facility is provided.