Definition

A. BASIC SUBJECT MATTER OF CLASS

This is the generic class for demodulators. A demodulator is a device which extracts an arbitrarily varying information carrying signal from a signal formed by varying a characteristic of a repetitious electrical or electromagnetic wave of less than infrared frequency in accordance with this information carrying signal. Classification herein is broadly by the type of modulation exhibited by the input signal.

B. COMBINATIONS WITH BASIC SUBJECT MATTER INCLUDED IN THIS CLASS

1. A demodulator combined with perfecting structure is classified here. Such structure might include, for example, a particular power supply for electronic devices within the demodulator.

2. A demodulator combined with or incorporated in other structure not otherwise classifiable is classified here. This might include, for example, a demodulator combined with an acoustical device such as a loudspeaker.

3. A combination including both a modulator and a demodulator is classified elsewhere. See Lines With Other Classes and Within This Class, below.

C. MISCELLANEOUS SYSTEMS AND DEVICES USED WITH DEMODULATORS

This class provides for (1) miscellaneous systems and devices which are not of general utility and which are limited to use with demodulators and (2) miscellaneous systems and devices useful with demodulators which are not otherwise classified. An example of this would be convertible demodulators which convert between different types of demodulators or which convert to or from devices other than demodulators.

Lines with other classes and within this class

A combination including both a modulator and a demodulator is classified in Class 332where such combination is not provided for elsewhere.

Excluded from this class are pulse code demodulators and delta modulation demodulators which are now classified elsewhere. See References to other Classes, below.

Several classes contain structure which is closely analogous to demodulators. Particularly significant among these is the art in the class for miscellaneous active electrical nonlinear devices, circuits, and systems. See the relevant SEARCH CLASS notes below in References to Other Classes in completing the search for subject matter of Class 329.

Many classes contain subject matter which includes demodulators or analogous devices as subcombinations thereof. Among these are receivers and complete communication systems (i.e., transmitters and receivers). (See References to Other Classes, below.)Therefore, these classes and others contained in the SEARCH CLASS notes below in References to Other Classes, should be considered in completing the search for subject matter of Class 329.

The terms "discriminator" and "detector" are often but not always used synonymously with "demodulator". Classification in Class 329 is appropriate where the terms "discriminator" or "detector" are recited and which clearly disclose a corresponding function of demodulation per the definition above. Classification is elsewhere where no such disclosure is present. See the SEARCH CLASS notes below in References to Other Classes, particularly those for the class for miscellaneous active electrical nonlinear devices, circuits, and systems.

Demodulators having a modulated input of less than infrared frequency which may utilize an internal optical element (e.g., an optical isolator) are classified in Class 329 by the type of modulation.

The combination of modulation converter (e.g., FM to AM) with a demodulator is classified in Class 329according to the modulation type of the input to the converter. Modulation converters, per se, are classified elsewhere. See References to Other Classes, below.

For classification herein there must be complete extraction of the modulating signal. Mere frequency converters (e.g., RF to IF mixers) are not classified here. See References to Other Classes, below.

Class 329 provides for demodulators, per se, with structure for noise or distortion control (see Subclass References to the Current Class, below). Class 455, Telecommunications, provides for noise or interference control in: (a) a telecommunication system (i.e., transmitter and receiver); (b) a complete telecommunication receiver; and (c) a combination of two or more receiver elements (viz. wave collector, wave mixer or modifier, demodulator, and utilization device) where the combination is not elsewhere classified. Therefore, consideration must be given to extending the search for demodulator noise control circuitry into relevant subclasses of Class 455. See also the SEARCH CLASS notes in References to Other Classes, below, relating to Class 455.

Subclasses of this class (329) relate to suppressed carrier double sideband demodulators, per se, and single/vestigial sideband demodulators, per se (see Subclass References to the Current Class, below). Class 455accepts this subject matter in combination with what may be broadly recited diverse receiver elements (viz. wave collector, wave modifier or mixer, and utilization device). Therefore, in completing the search for demodulators of an amplitude modulated wave not having the full complement of carrier and two complete sidebands, consideration must be given to extending the search to relevant subclasses in Class 455. See also the SEARCH CLASS notes in References to Other Classes, below, relating to Class 455.