Title: Modem for a suppressed carrier communications system

Abstract: A modem having a transmitter portion including a first modulator connected to receive audio frequency signals and supplying an output signal through a single sideband filter to a second modulator providing an output signal at a unique channel frequency, a receiver portion including a first demodulator connected to receive transmitted signals and supplying an output signal to a second demodulator through a single sideband filter with the second demodulator providing audio frequency output signals, a carrier switch supplying a small amount of the carrier to the second modulator during operation of the transmitter and a carrier level switch associated with the carrier switch for supplying the carrier at high and low levels, and a crystal controlled channel oscillator connected to the second modulator of the transmitter portion and the first demodulator of the receiver portion with removable, plugin crystals connected thereto for controlling the channel frequency of the modem.

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Inventors: Bates, Wayne J. (Des Plaines, IL, US)
Berenson, Walter L. (Palatine, IL, US)
Euchner, Jr., William H. (Arlington Heights, IL, US)
Grigg, James H. (Chicago, IL, US)
Stern, Morton (Skokie, IL, US)
Taylor, Ronald W. (Arlington Heights, IL, US)

Application Number: 534388
Filing Date: 1974-12-19
Publication_date: 1976-07-20
Assignee: Motorola, Inc. (Schaumburg, IL)
Primary Class(es): 455/46 455/47, 455/86, 455/109, 455/116, 455/202
Other Classes:
US Patent Ref:

2678384	May, 1954	Beers	325/55.
2974222	Mar, 1961	Lawson	325/50.
3042867	Jul, 1962	Thompson	325/50.
3147437	Sep, 1964	Crafts et al.	325/49.
3300720	Jan, 1967	Kowols	325/50.

Other Refs:
Primary Examiner: Griffin, Robert L.
Assistant Examiner: Hearn, Robert
Attorney: Gillman; James W., Parsons; Eugene A.