This sub-class deals with (a) generation of substantially sinusoidal oscillations directly or by frequency-changing, (b) regulation of generator output, (c) synchronisation of generator output and (d) generation of noise currents or voltages.
This sub-class deals only with modulation, keying, or interruption of sinusoidal oscillations or electromagnetic waves, the modulating signal having any desired waveform.
In this sub-class, circuits usable both as modulator and demodulator are classified in the group dealing with the type of modulator involved.
This sub-class deals only with (a) demodulation or transference of signals modulated on a sinusoidal carrier or on electromagnetic waves, and (b) comparing phase or frequency of two mutually-independent oscillations.
This sub-class deals with (a) linear amplification, there being linear relationship between the amplitudes of input and output, and the output having substantially the same waveform as the input, (b) dielectric amplifiers, magnetic amplifiers, and parametric amplifiers when used as oscillators or frequency-changers, and (c) constructions of active elements of dielectric amplifiers and parametric amplifiers for which no provision exists elsewhere.
This sub-class deals with (a) control of gain of amplifiers or frequency-changers, (b) control of frequency range of amplifiers, and (c) limiting amplitude or rate of change of amplitude.
This sub-class deals with (a) networks comprising lumped impedance elements, (b) networks comprising distributed impedance elements together with lumped impedance elements, (c) networks comprising electromechanical or electro-acoustic devices, (d) networks simulating reactances and comprising discharge tubes or semiconductor devices, and (e) constructions of electromechanical resonators.
This sub-class deals with (a) methods, circuits, devices, or apparatus for generating, counting, amplifying, shaping, modulating, demodulating, coding, decoding, or otherwise manipulating substantially non-sinusoidal oscillations, i.e. electric pulses, (b) electronic switching not involving contact-making and breaking, and (c) logic circuits handling electric pulses.
In this sub-class, an "active element" is understood to exercise control over the conversion of input energy into an oscillation or a discontinuous flow of energy.