(under subclass 2) Systems using alternating, pulsating,
sine, or similar wave currents in the transmission of messages, but excluding harmonic or reed systems (defined in subclass 47).
SEE OR SEARCH THIS CLASS, SUBCLASS:
49, for alternating current transmitting means employed in superposed current telegraphy.
63, for systems employing reversal of current and pole changers for reversing currents.
69, for prevention of leakage, induction, and "tailings" and for capacity compensation, etc., and not otherwise specific to duplex or a quadruplex or cable systems.
SEE OR SEARCH CLASS
329, Demodulators, appropriate subclasses for demodulators and detectors in general, particularly 311+, for pulse demodulators; and subclasses 315+, for frequency demodulators and 345+ for phase demodulators respectively.
330, Amplifiers, appropriate subclasses for various types of amplifiers.
331, Oscillators, appropriate subclasses for electrical oscillators in general, particularly
179, for step-frequency change oscillator systems (e.g., frequency shift type).
332, Modulators, appropriate subclasses for modulators, and particularly
117+, for frequency modulators, 144+ for phase modulators -- and -- 149+ --, respectively and subclasses 31+ for amplitude modulators.
375, Pulse or Digital Communications,
259+, for pulse or digital communication systems using alternating or pulsating current.
