26 INSTRUMENTS FOR MONITORING, MEASURING AND CONTROLLING CONDITIONS-NAMELY, SENSORS, SIGNAL MODULATORS AND INDICATORS RESPONSIVE TO CONDITION CHANGES INCLUDING TEMPERATURE, HUMIDITY, PRESSURE, HEAT, FLUID FLOW, POSITION, SETPOINT, FLAME, ETC.; HIGHEST, LOWEST, AND AVERAGE SIGNAL SELECTORS; CONDITION PROGRAMMERS; SIGNAL LIMITERS; SIGNAL AMPLIFIERS; LIMIT CONTROLLERS; ON-OFF CONTROLLERS; MODULATING AND TIME PROPORTIONING CONTROLLERS WITH AND WITHOUT AUTOMATIC RESET AND RATE ACTION; COMBUSTION SAFEGUARDS; CONTROL CENTERS, PANELS AND BOXES; ELECTROHYDRAULIC ACTUATORS; RECTIFIERS; SIGNAL CONVERTERS; AND REMOTE CONTROL AND MONITORING SYSTEMS EMPLOYING SAID INSTRUMENTS