26 SIGNAL PROCESSING UNITS AND INDICATING INSTRUMENTS-NAMELY, CHARGE AMPLIFIERS, LOOP AMPLIFIERS, DISCRIMINATORS, INTEGRATORS, DIFFERENTIATORS, SUMMING UNITS, CHARGE CALIBRATORS, SELECTORS, PEAK METERS, CLASSIFYING INSTRUMENTS, COMPENSATORS, AND ELECTRICAL AND ELECTRONIC ELEMENTS THEREOF, CALIBRATION CONDENSORS, FINE BALANCING EQUIPMENT, SERVO SYSTEMS; CONTROL EQUIPMENT FOR THE CONTROL OF CYLINDER PRESSURES AND FLUID PRESSURES OF ENGINES AND GAS TURBINES AS USED ON VEHICLES, AEROPLANES, VESSELS AND STATIONARY POWER INSTALLATIONS; ACCELEROMETERS AND ACCELEROMETERS FOR TWO- AND MULTI-COMPONENT MEASUREMENTS; CONTROL-REGULATING, AND MONITORING SYSTEMS FOR MACHINE TOOLS TO CONTROL OVERLOADING THEREOF, AND TEST APPARATUS FOR TRANSDUCERS