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Class Number: 375 Class Title: PULSE OR DIGITAL COMMUNICATIONS Subclass Subclass Number Title 1 SPREAD SPECTRUM 3 REPEATERS 3.1 .Testing 4 .Including pulse regeneration or conversion 5 APPARATUS CONVERTIBLE TO ANALOG 6 EARTH OR WATER MEDIUM 7 TRANSCEIVERS 8 .Modems (data sets) 9 ..Angle modulation 10 TESTING 11 EQUALIZERS 12 .Automatic 13 ..Training period or initial set up 14 ..Adaptive 15 ...Quadrature channels 16 ...Accumulator or up/down counter 17 MULTILEVEL 18 .Partial response 19 .Disparity reduction 20 .Synchronized 21 PULSE NUMBER MODULATION 22 PULSE WIDTH MODULATION 23 PULSE POSITION, FREQUENCY, OR SPACING MODULATION 24 PULSE AMPLITUDE MODULATION 25 PULSE CODE MODULATION 26 .Correcting or reducing quantizing errors 27 .Differential 28 ..Single bit (delta) 29 ...Nonamplitude delta (area, etc.) 30 ...Compand (overload prevention) 31 ....Redundancy Removal 32 ....Syllabic 33 ...Plural feedback loops 34 .Noise or distortion reduction 122 BANDWIDTH REDUCTION OR EXPANSION 35 PULSE TRANSMISSION VIA RADIATED BASEBAND 36 CABLE SYSTEMS AND COMPONENTS 37 SYSTEMS USING ALTERNATING OR PULSATING CURRENT 38 .Plural channels for transmission of a single pulse train 39 ..Quadrature amplitude modulation 40 ..Diversity 41 .Amplitude modulation 42 ..With phase or frequency shift keying 43 ..Vestigial or single sideband or suppressed carrier 44 .Angle modulation 45 ..Frequency shift keying 46 ...Combined with phase shift keying 47 ...Minimum shift keying 48 ...More than two frequencies 49 ...One cycle or less per bit 50 ...Vestigial or single sideband, or suppressed carrier 51 ...Anti-noise or distortionn 52 ..Phase shift keying 53 ...More than two phases 54 ....Quaternary 55 ...Biphase (manchester codes) 56 ...Differential phase shift keying (diphase) 57 ...Antinoise or distortion 58 .Antinoise or distortion 59 TRANSMITTERS 60 .Antinoise or distortion (includes predistortion) 61 .Single or vestigial sideband or suppressed carrier 62 .Frequency shift keying 63 ..Antenna tuning with frequency shift 64 ..Minimum shift keying 65 ..One oscillator 66 ..Two or more oscillators 67 .Phase shift keying 68 .Keying circuits 69 ..Remote controlled 70 ..Automatic 71 ..Power or bias voltage supply keying 72 ..Key shock or click prevention 73 ..Including auxiliary control tube 74 ..Modulation by absorption of signal, changing antenna dimension or changing antenna impedance 75 RECEIVERS 76 .Automatic baseline or threshold adjustment 77 .Single or vestigial sideband or suppressed carrier 78 .Angle modulation 79 ..Combined phase shift keyed and frequency shift keyed 80 ..Particular demodulator 81 ...Phase locked loop 82 ...Including switching or gating (digital circuits) 83 ..Phase shift keying 84 ...Differential (diphase) 85 ....More than two phases 86 ...Plural phase (>2) 87 ...Biphase (manchester code) 88 ..Frequency shift keying 89 ...More than two frequencies 90 ...Minimum shift keying 91 ...Separate mark and space channels 92 .Interrupted carrier wave 93 ..Carrier controlling local generator 94 .Particular pulse demodulator or detector 95 ..Locating predetermined portion of pulse 96 ..Correlative or matched filter 97 .Automatic frequency control 98 .Automatic gain control 99 .Interference or noise reduction 100 ..Diversity (frequency or time) 101 ..Intersymbol interference 102 ..Plural signal paths in receiver 103 ..By filtering (e.g., digital) 104 ..Gating, blanking, etc. 105 .With elctromagnetic relay or solenoid 106 SYNCHRONIZERS 107 .Network synchronizing more than two stations 108 .Synchronization failure preventionn 109 .Feedback, receiver to transmitter 110 .Self synchronizing signal (self clocking codes, etc.) 111 .Frequency or phase control using synchronizing signal 112 ..Synchronization bit insertion into artificially created gaps 113 ..Synchronization signals with unique amplitude, polarity, length or frequency 114 ..Synchronization word 115 ...Pseudo noise 116 ...Synchronizer pattern recognizers 117 ..Start - stop 118 .Phase displacement, slip or jitter correction 119 ..Phase locking 120 ...Phase locked loop 121 MISCELLANEOUS