Abstract: A removable rating plug for a circuit breaker provides an active variable impedance in series with a reference resistor between the sensing terminals of the circuit breaker trip circuit to adjust the sensing voltage produced in response to the input current received from current monitors in the protected circuit. The active variable impedance, which is energized by the input current, includes a high gain transistor amplifier, preferably a Darlington transistor, controlled by an operational amplifier. A control circuit includes a pair of reference diodes which match the forward drop across the Darlington transistor when full on, in series with a reference voltage selection circuit which applies a reference voltage to the non-inverting input of the operational amplifier.

Abstract: Novel 2-oxopyrrolidine compounds represented by the formula ##STR1## wherein R.sup.1 and R.sup.2 are hydrogen or alkyl group, respectively, A is alkylene group or phenyl substituted alkylene group, and B is alkylene group,or a salt thereof, a process for the preparation thereof, and a pharmaceutical agent comprising the compound or salt as an effective component.