ACB (Under Voltage, Tripping and Closing Coil Fitting) make: Schneider.....

An under voltage release is an optional device installed in a circuit breaker that automatically triggers a power trip when the power falls below a preset level, usually between 70 and 35 percent of the UV rating. The circuit breaker does not power it. Instead, it receives its power from an alternative source, such as a battery. It was initially designed for use in coal mines but can now be found in any field employing heavy industry./ And closing coil only ON operation and Tripping coil only Off operation Used.