US Patent Class 375
PULSE OR DIGITAL COMMUNICATIONS



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Current as of: June, 1999
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  DF  CLASS NOTES
200  DF  SPREAD SPECTRUM
201  DF  .~ Hybrid forms
202  DF  .~ Frequency hopping
203  DF  .~ Time hopping
204  DF  .~ Pulsed FM or chirp
206  DF  .~ Direct sequence
207  DF  .~ Matched filter
208  DF  .~ Pseudo-noise correlation
209  DF  .~.~ Auto-correlation
210  DF  .~.~ Cross-correlation
211  DF  REPEATERS
212  DF  .~ Ring or star configuration
213  DF  .~ Testing
214  DF  .~ Including pulse regeneration or conversion
215  DF  .~.~ Phase locked loop
216  DF  APPARATUS CONVERTIBLE TO ANALOG
217  DF  .~ Muting circuit and squelch
218  DF  EARTH OR WATER MEDIUM
219  DF  TRANSCEIVERS
220  DF  .~ Transmission interface between two stations or terminals
221  DF  .~ Loopback mode
222  DF  .~ Modems (data sets)
223  DF  .~.~ Angle modulation
224  DF  TESTING
225  DF  .~ Data rate
226  DF  .~ Phase error or phase jitter
227  DF  .~ Signal noise
228  DF  .~ With indicator
229  DF  EQUALIZERS
230  DF  .~ Automatic
231  DF  .~.~ Training period or initial set up
232  DF  .~.~ Adaptive
233  DF  .~.~.~ Decision feedback equalizer
234  DF  .~.~.~ Fractionally spaced equalizer
235  DF  .~.~.~ Quadrature channels
236  DF  .~.~.~ Accumulator or up/down counter
237  DF  PULSE NUMBER MODULATION
238  DF  PULSE WIDTH MODULATION
239  DF  PULSE POSITION, FREQUENCY, OR SPACING MODULATION
240  DF  BANDWIDTH REDUCTION OR EXPANSION
241  DF  .~ Pulse code modulation
242  DF  PULSE CODE MODULATION
243  DF  .~ Correcting or reducing quantizing errors
244  DF  .~ Differential
245  DF  .~.~ Quantizer or inverse quantizer
246  DF  .~.~ Length coding
247  DF  .~.~ Single bit (delta)
248  DF  .~.~.~ Nonamplitude delta (area, etc.)
249  DF  .~.~.~ Compand (overload prevention)
250  DF  .~.~.~.~ Redundancy removal
251  DF  .~.~.~.~ Syllabic
252  DF  .~.~.~ Plural feedback loops
253  DF  .~ Length coding
254  DF  .~ Noise or distortion reduction
256  DF  PULSE TRANSMISSION VIA RADIATED BASEBAND
257  DF  CABLE SYSTEMS AND COMPONENTS
258  DF  .~ Transformer coupling
259  DF  SYSTEMS USING ALTERNATING OR PULSATING CURRENT
260  DF  .~ Plural channels for transmission of a single pulse train
261  DF  .~.~ Quadrature amplitude modulation
262  DF  .~.~.~ Maximum likelihood decoder or viterbi decoder
263  DF  .~.~.~ Partial response
264  DF  .~.~.~ Multilevel
265  DF  .~.~.~ Trellis encoder or Trellis decoder
267  DF  .~.~ Diversity
268  DF  .~ Amplitude modulation
269  DF  .~.~ With phase or frequency shift keying
270  DF  .~.~ Vestigial or single sideband or suppressed carrier
271  DF  .~ Angle modulation
272  DF  .~.~ Frequency shift keying
273  DF  .~.~.~ Combined with phase shift keying
274  DF  .~.~.~ Minimum shift keying
275  DF  .~.~.~ More than two frequencies
276  DF  .~.~.~ One cycle or less per bit
277  DF  .~.~.~ Vestigial or single sideband, or suppressed carrier
278  DF  .~.~.~ Antinoise or distortion
279  DF  .~.~ Phase shift keying
280  DF  .~.~.~ More than two phases
281  DF  .~.~.~.~ Quaternary
282  DF  .~.~.~ Biphase (manchester codes)
283  DF  .~.~.~ Differential phase shift keying (diphase)
284  DF  .~.~.~ Antinoise or distortion
285  DF  .~ Antinoise or distortion
286  DF  MULTILEVEL
287  DF  .~ With threshold level
288  DF  .~ Transmission line
289  DF  .~ Bipolar signal
290  DF  .~ Partial response
291  DF  .~.~ Duobinary
292  DF  .~ Disparity reduction
293  DF  .~ Synchronized
294  DF  .~.~ Phase locked loop
295  DF  TRANSMITTERS
296  DF  .~ Antinoise or distortion (includes predistortion)
297  DF  .~.~ Power amplifier
298  DF  .~ Quadrature amplitude modulation
299  DF  .~ Plural diversity
300  DF  .~ Amplitude modulation
301  DF  .~.~ Single or vestigial sideband or suppressed carrier
302  DF  .~ Angle modulation
303  DF  .~.~ Frequency shift keying
304  DF  .~.~.~ Antenna tuning with frequency shift
305  DF  .~.~.~ Minimum shift keying
306  DF  .~.~.~ One oscillator
307  DF  .~.~.~ Two or more oscillators
308  DF  .~.~ Phase shift keying
309  DF  .~ Keying circuits
310  DF  .~.~ Remote controlled
311  DF  .~.~ Automatic
312  DF  .~.~ Power or bias voltage supply keying
313  DF  .~.~ Key shock or click prevention
314  DF  .~.~ Including auxiliary control tube
315  DF  .~.~ Modulation by absorption of signal, changing antenna dimension or changing antenna impedance
316  DF  RECEIVERS
317  DF  .~ Automatic baseline or threshold adjustment
318  DF  .~.~ Differential amplifier
319  DF  .~.~ Automatic bias circuit for DC restoration
320  DF  .~ Amplitude modulation
321  DF  .~.~ Single or vestigial sideband or suppressed carrier
322  DF  .~ Angle modulation
323  DF  .~.~ Combined phase shift keyed and frequency shift keyed
324  DF  .~.~ Particular demodulator
325  DF  .~.~.~ Including coherent detector
326  DF  .~.~.~ Carrier recovery circuit or carrier tracking
327  DF  .~.~.~ Phase locked loop
328  DF  .~.~.~ Including switching or gating (digital circuits)
329  DF  .~.~ Phase shift keying
330  DF  .~.~.~ Differential (diphase)
331  DF  .~.~.~.~ More than two phases
332  DF  .~.~.~ Plural phase (>2)
333  DF  .~.~.~ Biphase (manchester code)
334  DF  .~.~ Frequency shift keying
335  DF  .~.~.~ More than two frequencies
336  DF  .~.~.~ Minimum shift keying
337  DF  .~.~.~ Separate mark and space channels
338  DF  .~ Interrupted carrier wave
339  DF  .~.~ Carrier controlling local generator
340  DF  .~ Particular pulse demodulator or detector
341  DF  .~.~ Maximum likelihood decoder or viterbi decoder
342  DF  .~.~ Locating predetermined portion of pulse
343  DF  .~.~ Correlative or matched filter
344  DF  .~ Automatic frequency control
345  DF  .~ Automatic gain control
346  DF  .~ Interference or noise reduction
347  DF  .~.~ Diversity (frequency or time)
348  DF  .~.~ Intersymbol interference
349  DF  .~.~ Plural signal paths in receiver
350  DF  .~.~ By filtering (e.g., digital)
351  DF  .~.~ Gating, blanking, etc.
352  DF  .~ With electromagnetic relay or solenoid
353  DF  PULSE AMPLITUDE MODULATION
354  DF  SYNCHRONIZERS
355  DF  .~ Synchronizing the sampling time of digital data
356  DF  .~ Network synchronizing more than two stations
357  DF  .~ Synchronization failure prevention
358  DF  .~ Feedback, receiver to transmitter
359  DF  .~ Self-synchronizing signal (self-clocking codes, etc.)
360  DF  .~.~ With transition detector
361  DF  .~.~ Manchester code or biphase code
362  DF  .~ Frequency or phase control using synchronizing signal
363  DF  .~.~ Synchronization bit insertion into artificially created gaps
364  DF  .~.~ Synchronization signals with unique amplitude, polarity, length, or frequency
365  DF  .~.~ Synchronization word
366  DF  .~.~.~ Plurality of synchronization words
367  DF  .~.~.~ Pseudo noise
368  DF  .~.~.~ Synchronizer pattern recognizers
369  DF  .~.~ Start - stop
370  DF  .~.~.~ With asynchronous data
371  DF  .~ Phase displacement, slip or jitter correction
372  DF  .~.~ Elastic buffer
373  DF  .~.~ Phase locking
374  DF  .~.~.~ With charge pump or up and down counters
375  DF  .~.~.~ With frequency detector and phase detector
376  DF  .~.~.~ Phase locked loop
377  DF  MISCELLANEOUS