Control units used in EMCom protect power circuits. They also offer measurements, display, communication and current maximeters. Control units measure the true (rms) value of currents. They provide continuous current measurements from 0.2 to 1.2 In and are accurate to within 1.5 % (including the sensors). A digital LCD screen continuously displays the most heavily loaded phase (Imax) or displays the I1, I2, I3, IN, Ig,I∆n, stored-current (maximeter) and setting values by successively pressing the navigation button. The optional external power supply makes it possible to display currents < 20 % In. Below 0.1 In, measurements are not significant. Between 0.1 and 0.2 In, accuracy changes linearly from 4 % to 1.5 %. In addition to the ammeter measurements control units measure and display: current demand, voltages - phase to phase, phase to neutral, average and unbalanced, instantaneous power - P, Q, S, power factor - PF, power demand - P demand, energy - Ep, Eq, Es. Accuracy of active energy Ep is 2 % (including the sensors). In conjunction with the COM communication option, the control units transmit the following: settings all ammeter and energy measurements, enable connection to FDM and energy servers, tripping causes, maximeter / minimeter readings.