Security communication system using polarity inversion

Details Security communication system using polarity inversion Security communication system using polarity inversion

1977-09-29

1979-06-26

Birmiel, Howard A.

179 15R, H04K 102, H04K 108

Patent

active

041593995

ABSTRACT:
In a security communication system, the transmitting unit includes a sample - hold circuit for sampling and holding the original voice signal, an inverting circuit for inverting the polarity of the samples of the voice signal in accordance with a first code, an adder circuit for adding a D.C. signal to the output signal of the inverting circuit, and another inverting circuit for inverting the polarity of the samples of the output signal of the adder circuit in accordance with a second code. The receiving unit includes a sample - hold circuit for sampling and holding the received signal, a synchronizing circuit for extracting a synchronizing signal component from a received signal during, for example a period of non-voice transmission, and for synchronizing the transmitting unit with the receiving unit, an inverting circuit for inverting the polarity of the samples of the received signal in accordance with the second code, a circuit for removing a D.C. signal component from the output of the inverting circuit, and a polarity inverting circuit for restoring the received signal from which the D.C. signal has been removed by said removing circuit to the original voice signal through the polarity inversion of the received signal in accordance with a third code.

REFERENCES:
patent: 3180927 (1965-04-01), Heppe et al.
patent: 3723878 (1973-03-01), Miller
patent: 3740477 (1973-06-01), Switsen
patent: 3824468 (1974-07-01), Zegers
patent: 3893031 (1975-07-01), Majeau et al.
patent: 3909534 (1975-09-01), Majeau et al.

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