[ LOAD CELLS; PORTABLE WEIGHING PLATFORMS; DIGITAL WEIGHT INDICATORS; ] MASS FUEL FLOWMETERING SYSTEMS AND COMPONENTS THEREOF-NAMELY, FUEL USED INDICATORS, MASS FLOW RATE INDICATORS, MASS FUEL FLOW TRANSMITTERS, MASS FUEL FLOW SIGNAL CONDITIONERS, FUEL USED AND MASS FUEL FLOW SIGNAL CONDITIONERS AND POWER SUPPLIES, FUEL USED INDICATOR TESTERS, MASS FUEL FLOW SIGNAL CONDITIONER TESTERS, MASS FLOW RATE INDICATOR TESTERS, AND MASS FUEL FLOW TRANSMITTER SPRING TEST AND BALANCE FIXTURES; JET ENGINE INSTRUMENTATION VERTICAL SCALE INDICATORS; EDDY CURRENT LOSS, VARIABLE RELUCTANCE AND OPTICAL PROXIMITY SWITCHES; LINEAR EDDY CURRENT LOSS PROXIMITY SENSORS; PROXIMITY SENSOR AND SWITCH TEST SETS; LOGIC AND CONTROL SYSTEMS FOR INTERFACING BETWEEN PROXIMITY SENSORS OR SWITCHES AND OTHER CONTROL CIRCUITS; [ ON-BOARD VEHICLE MAGNETOMETER APPARATUS FOR DETECTING PROXIMITY OF THE VEHICLE TO ONE OF A PLURALITY OF MAGNETS LOCATED ON THE VEHICLE'S TRACK; STRAIN GAUGE MEASUREMENT SYSTEMS; ] PRESSURE TRANSDUCERS; AC AND DC SIGNAL CONDITIONING AMPLIFIERS; ANALOG DATA ACQUISITION UNITS INCLUDING SIGNAL CONDITIONING MODULES-NAMELY, DC AMPLIFIERS, PULSE RATE-TO-DC CONVERTERS, RESISTANCE-TO-DC CONVERTERS, AC-TO-DC CONVERTERS, AC VOLTAGE-TO-DC CONVERTERS, DC VOLTAGE-TO-DIGITAL LOGIC LEVEL CONVERTERS, AND AC VOLTAGE-TO-DIGITAL LOGIC LEVEL CONVERTERS USED, FOR EXAMPLE, IN SPACE VEHICLE AND SATELLITE CONTROL SYSTEMS; CHARGE AMPLIFIERS; DC VOLTAGE BOOSTERS; BATTERY CHARGES, DC POWER SUPPLIES; [ THERMOSTATIC WATER HEATER CONTROLS; ] INCANDESCENT LAMP CONTROL DIMMERS [ ; JET ENGINE CONTROL PANELS FOR STARTING, OPERATING, SHUTTING DOWN, AND MONITORING VARIOUS CONDITIONS OF A GAS TURBINE JET ENGINE USED IN MARINE INSTALLATIONS; ON-BOARD ELECTRONIC ALARM UNITS FOR PROVIDING AN AUDIBLE ALARM UPON REVERSE MOTION OF A VEHICLE; ONBOARD VEHICLE LOAD WEIGHING SYSTEMS; AIRCRAFT WEIGHT AND BALANCE MEASURING SYSTEMS AND COMPONENTS THEREOF-NAMELY, AIRCRAFT WEIGHT AND BALANCE COMPUTERS AND INDICATORS, AIRCRAFT WEIGHT TRANSDUCERS, AIRCRAFT ATTITUDE SENSORS, AIRCRAFT WEIGHT AND BALANCE COMPUTER AND INDICATOR TEST SETS, AND AIRCRAFT ATTITUDE SENSOR TEST SETS; INTERVAL TIMERS; TIME DELAY SWITCHES; AND ELAPSED TIME INDICATORS ]