Telegraphy – Systems – Alternating or pulsating current
Patent
1974-10-18
1977-07-19
Griffin, Robert L.
Telegraphy
Systems
Alternating or pulsating current
325 30, H04L 2718
Patent
active
040370496
ABSTRACT:
A modem with transmitter and receiver sections. Incoming digital data signals produce successive coordinate signals to define successive transmission points representing a given digital value and to modulate quadrature carrier signals. The coordinate signals have unit values of 0, 1, 2.707, 3 and 5 and together control the amplitude and phase of the modulated carrier signals. The receiver section uses received coordinate signals, after they are properly conditioned, to select a decision region which corresponds to a transmission point to produce the digital data signals. The decision regions have rectilinear boundaries on a Cartesian coordinate system at unit values 0, 1.25, 2 and 4 and each region is either rectangular or non-rectangular. Digital synchronism between separate modems is maintained by transmitting coordinate signals corresponding to a framing point which is separate from the transmission points, but which has the same digital value as a transmission point. Certain decision regions defined by the receiver use the receipt of the modulated carrier signals corresponding to a framing point to initiate a synchronizing operation.
REFERENCES:
patent: 3706945 (1972-12-01), Yanagidaira et al.
patent: 3764743 (1973-10-01), Melvin
patent: 3805191 (1974-04-01), Kawai et al.
patent: 3845412 (1974-10-01), Rearwin
patent: 3887768 (1975-06-01), Forney, Jr.
Griffin Robert L.
Intertel, Inc.
Masinick Michael A.
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