Data transmission system

Details Data transmission system Data transmission system

1974-12-09

1977-10-04

Griffin, Robert L.

Telegraphy

Systems

Chemical

178 88, 325 38R, 325320, 325351, 307216, H04B 100

Patent

active

040525589

ABSTRACT:
A modem adapted to enable data transmission over information communication links, such as a voice-grade telephone line. The modem includes a modulator where a binary data source and a clock pulse source are connected to an exclusive OR gate which provides an output pulse train including pulses having widths which are a function of the binary data. The pulse train is applied to a flip-flop and thereafter the output of the flip-flop is introduced into a low-pass filter to provide a sinusoidally varying frequency signal. This signal from the low-pass filter is demodulated by a demodulator circuit which in a first embodiment of the present invention employs a counter implemented in the form of digital circuitry. In a second embodiment of the present invention, this demodulator includes a shift register operating in conjunction with a phase locked loop and a controlled oscillator.

REFERENCES:
patent: 3462702 (1969-08-01), McCormick
patent: 3590384 (1971-06-01), Van Gerwen
patent: 3611143 (1971-10-01), Van Gerwen
patent: 3699447 (1971-10-01), Frost
patent: 3758870 (1973-09-01), Schmitt et al.
patent: 3846583 (1974-11-01), Boulter

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