| | CLASS NOTES |
| 1 R | DF | WITH DIVERSE-TYPE ART DEVICE {1} |
| 2 | DF | WITH AMPLIFIER CONDITION INDICATING OR TESTING MEANS |
| 3 | DF | WITH PLURAL DIVERSE-TYPE AMPLIFYING DEVICES |
| 4 | DF | WITH MASER-TYPE AMPLIFYING DEVICE |
| 4.5 | DF | PARAMETRIC AMPLIFIERS {3} |
| 5 | DF | WITH SOLID ELEMENT WAVE PROPAGATING AMPLIFYING DEVICE {1} |
| 6 | DF | WITH HALL EFFECT TYPE MEANS |
| 7 | DF | WITH CAPACITIVE AMPLIFYING DEVICE |
| 8 | DF | WITH SATURABLE REACTOR-TYPE AMPLIFYING DEVICE |
| 9 | DF | WITH PERIODIC SWITCHING INPUT-OUTPUT (E.G., FOR DRIFT CORRECTION) |
| 10 | DF | MODULATOR-DEMODULATOR-TYPE AMPLIFIER |
| 11 | DF | WITH D.C. REINSERTION CIRCUIT |
| 250 | DF | WITH SEMICONDUCTOR AMPLIFYING DEVICE (E.G., TRANSISTOR) {21} |
| 41 | DF | WITH GAS OR VAPOR TUBE AMPLIFYING DEVICE |
| 42 | DF | WITH SECONDARY ELECTRON EMISSION TUBE AMPLIFYING DEVICE |
| 43 | DF | WITH TRAVELING WAVE-TYPE TUBE |
| 44 | DF | WITH ELECTRON BEAM TUBE AMPLIFYING DEVICE {2} |
| 47 | DF | WITH MAGNETICALLY INFLUENCED DISCHARGE DEVICE (E.G., MAGNETRONS) {1} |
| 49 | DF | WITH VACUUM TUBE HAVING DISTRIBUTED PARAMETER IMPEDANCE CHARACTERISTICS |
| 50 | DF | WITH DUMMY TUBE |
| 51 | DF | COMBINED WITH AUTOMATIC AMPLIFIER DISABLING SWITCH MEANS |
| 52 | DF | WITH PILOT FREQUENCY CONTROL MEANS |
| 53 | DF | WITH DISTRIBUTED PARAMETER-TYPE COUPLING MEANS {4} |
| 58 | DF | WITH ROTATING DYNAMOELECTRIC AMPLIFYING DEVICE |
| 59 | DF | HAVING LIGHT-CONTROLLED OR ACTIVATED DEVICE (I.E., NOT LIGHT SIGNAL) |
| 60 | DF | HAVING MAGNETOSTRICTIVE-TYPE AMPLIFYING DEVICE |
| 61 R | DF | WITH RESISTIVE-TYPE AMPLIFYING DEVICE {2} |
| 63 | DF | WITH MAGNETIC MEANS AMPLIFYING DEVICE |
| 64 | DF | WITH SPACE CHARGE GRID TUBE |
| 65 | DF | INVOLVING STRUCTURE OTHER THAN THAT OF TRANSFORMERS PER SE {3} |
| 69 | DF | SUM AND DIFFERENCE AMPLIFIERS |
| 70 | DF | ANODE ENERGIZED THROUGH DISCHARGE PATH OF CONTROLLED VACUUM TUBE {3} |
| 75 | DF | SIGNAL FEEDBACK {20} |
| 113 | DF | POLYPHASE POWER SUPPLY (I.E., FOR AN ELECTRODE, CATHODE HEATER, OR FILAMENT) |
| 114 | DF | UNRECTIFIED A.C. POWER SUPPLY FOR AN ELECTRODE (I.E., NOT THE HEATER) {1} |
| 116 | DF | WITH BALANCED-TO-UNBALANCED COUPLING |
| 117 | DF | WITH UNBALANCED-TO-BALANCED COUPLING |
| 118 | DF | INCLUDING A PUSH-PULL STAGE {4} |
| 124 R | DF | WITH PLURAL AMPLIFIER CHANNELS (E.G., PARALLEL AMPLIFIER CHANNELS) {3} |
| 127 | DF | WITH CONTROL OF POWER SUPPLY OR BIAS VOLTAGE {2} |
| 143 | DF | THERMALLY RESPONSIVE IMPEDANCE |
| 144 | DF | VARIABLE IMPEDANCE FOR SIGNAL CHANNEL CONTROLLED BY SEPARATE CONTROL PATH {1} |
| 146 | DF | WHEATSTONE BRIDGE WITH AMPLIFIER IN AT LEAST ONE ARM |
| 147 | DF | PLURAL SIGNAL INPUTS |
| 148 | DF | PLURAL SIGNAL OUTPUTS |
| 149 | DF | HUM OR NOISE OR DISTORTION BUCKING INTRODUCED INTO SIGNAL CHANNEL |
| 150 | DF | CASCADED SIMILAR AMPLIFYING DEVICE OF DIFFERENT CHARACTERISTICS |
| 151 | DF | WITH AMPLIFIER BYPASS MEANS (E.G., FORWARD FEED) |
| 152 | DF | CASCADED DIFFERENTLY COUPLED BETWEEN STAGES {2} |
| 155 | DF | UNICONTROL OF COUPLING OR THE CIRCUITS ASSOCIATED THEREWITH |
| 156 | DF | BOOTSTRAP COUPLING |
| 157 | DF | INTERSTAGE COUPLING {11} |
| 185 | DF | INPUT NETWORKS {3} |
| 192 | DF | OUTPUT NETWORKS {3} |
| 199 | DF | WITH POWER OR BIAS VOLTAGE SUPPLY {4} |
| 207 R | DF | MISCELLANEOUS {2} |
