.~ Frequency domain filters utilizing only lumped parameters

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167.~ Frequency domain filters utilizing only lumped parameters {10}
168  DF  .~.~> Including recurrent sections
169  DF  .~.~> Wheatstone or lattice type
170  DF  .~.~> Bridge type {1}
172  DF  .~.~> RC or RL type
173  DF  .~.~> Synchronous filters
174  DF  .~.~> With variable response
175  DF  .~.~> Resonant, discrete frequency selective type {1}
177  DF  .~.~> Transformer coupled {3}
181  DF  .~.~> Smoothing type (e.g., direct current power supply filters or decoupling filters) {2}
185  DF  .~.~> Having significant physical structure


Classification: 333/167

Frequency domain filters utilizing only lumped parameters:

(under subclass 24) Subject matter having only parameters which may be considered as concentrated at one point and permitting free transmission of electric waves of a single frequency or band of frequencies (which may include zero frequency) while attenuating substantially electric waves having other frequencies, or attenuating substantially electric waves of a single frequency or band of frequencies (which may include zero frequency) while permitting free transmission of electric waves having other frequencies, and systems within the class definition which include such networks.

(1) Note. Tuners, which are closely analogous to the wave filters in this class, are classified in Class 334, Tuners. The tuners usually found in Class 334 consist of a lumped inductance and capacitance element together with structure means to vary either or both elements in order to change the mean resonant frequency of the tuner. The tuners in Class 334 may include one or more long line elements in addition to a lumped inductance or capacitance element, or the tuner may consist of a distributed parameter type tuning unit which is adjusted in discrete, distinct steps. Two or more distributed parameter type tuner units which are of the continuously variable type and which are ganged together mechanically and/or electrically so as to have their mean resonant frequency adjusted in unison are properly classified in Class 334. Where only the bandwidth of the filter is varied without varying the mean resonant frequency, classification is in this class (333).

(2) Note. Filters combined with circuits having other functions classified in other classes are excluded and will

be bound in other classes. See the classes referred to under "Search Class" below. Note the exception in the case of a mere current and or voltage control network combined with a filter in (4) Note.

(3) Note. Filters which include an active element are excluded. See Class 327, particularly subclasses 552+ where the active element is an electron tube or a transistor. Note that Class 327 includes some transversal filters.

(4) Note. Filters in combination with means merely to control the magnitude of the current and/or voltage in the network are included in this and the indented subclasses.


1+, for plural channel systems which include filters and for filters with plural input and/or output terminals. 19, for differentiating or integrating networks which are analogous to wave filters.

20, for wave shaping networks which are analogous to wave filters and which may include wave filters.

28, for equalizing networks which are analogous to wave filters.

100+, where the filter includes branching means (e.g., a single input with plural outputs).

124+, for resonant filter networks for matching the impedance in branched circuits, and branched circuits with line sections analogous to wave filters for impedance matching purposes.

157+, for delay networks which are analogous to wave filters.

202+, for long lines having frequency discriminating properties.

219+, for resonators including those with tuning means.


74, Machine Element or Mechanism,

1, for mechanical wave filters for transmitting mechanical waves of a particular frequency or band of frequencies.

84, Music, 1.19+, 621, 622, 699+ or 736 for electrical systems used in musical instruments to produce musical tones which include wave filters or tuners.

178, Telegraphy,

2+, for telegraph systems involving wave filters; and particularly subclass 47 and indented subclasses for harmonic or reed type selective systems; subclass 49 for superposed current systems with frequency selection means.

181, Acoustics,

175+, for sound filters.

307, Electrical Transmission or Interconnection Systems, particularly

105, for electrical distribution systems including wave filters and subclass 132 for circuit interrupting systems having filters to eliminate the higher frequency components.

322, Electricity: Single Generator Systems,

58, for generator controls with means for suppressing or minimizing undesired frequencies.

323, Electricity: Power Supply or Regulation Systems. Note that Class 323 provides for "filters" which control only the voltage and/or current magnitude. If the circuit which performs the filtering action is arranged only to "buck out" or balance the undesired components, classification is in Class 323.

327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, particularly 552+, for unwanted signal suppression by an active filter which may utilize a transistor or an electron tube.

329, Demodulators, appropriate subclasses for a demodulator which includes tuning or filtering.

330, Amplifiers,

302+, for transistor amplifiers with frequency responsive means; subclass 86 for amplifiers having an automatically variable impedance in the feedback path; subclass 94 for amplifiers having a frequency responsive means in a cathode feedback path; subclass 109 for amplifiers with frequency responsive means in the feedback path; subclass 143 for amplifiers with a thermal impedance in the signal path which may be automatically variable; subclasses 144+ for amplifiers having an automatically variable impedance in the signal path including such subject matter involving a variable reactance for automatically tunable or selective circuits; subclass 154 for cascaded amplifiers including a resonant circuit; subclass 155 for amplifier circuits including means for unicontrol of the coupling circuits; and subclasses 157+ and 192+ for amplifier systems with significant interstage, input and output coupling which may include wave filters.

331, Oscillators, appropriate subclasses, particularly

43, 76, 77, 110, and 138+ for oscillators utilizing a wave filter as an element thereof.

332, Modulators, appropriate subclasses for modulators involving wave filters.

340, Communications: Electrical,

825.71+, for selective communication systems which are frequency responsive.

343, Communications: Radio Wave Antennas,

722, for antennas with a lumped reactance filter in the active antenna; and subclasses 745+ for antennas with a variable reactance for tuning the antenna. 363, Electric Power Conversion Systems,

39+, for conversion systems in combination with a filter.

370, Multiplex Communications, appropriate subclasses, particularly

488, and 497 for a multiplex system which includes connecting filters.

379, Telephonic Communications, appropriate subclasses for telephone systems involving wave filters; and particularly

2, and indented subclasses for composite systems utilizing wave filters; and subclasses 78, 79, 80, and 174 for anti-inductive systems and devices with wave discriminating properties.

381, Electrical Audio Signal Processing Systems and Devices,

98+, for audio signal processing devices and systems having frequency control.

455, Telecommunications,

91+, for transmitters involving wave filters; and subclasses 150.1+ and 296+ (especially subclass 307) for radio receivers with filters or tuners.