Television system transmitting enciphered data signals during fi

Details Television system transmitting enciphered data signals during fi Television system transmitting enciphered data signals during fi

1976-11-08

1980-05-27

Martin, John C.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

H04N 708

Patent

active

042053439

ABSTRACT:
A television system for broadcasting data simultaneously with but independently of television programs, in which digitally coded information carrying signals are superimposed or otherwise added to a video system in the field blanking interval. The local receiver is fitted with a decoder by means of which a viewer is able to select a particular page of supplementary information which is then superimposed over the broadcast program. Generally, this information is available to any member of the public who has a requisite decoder. In this system the digitally coded information carrying signals are enciphered prior to transmission in accordance with a predetermined key and the receiving terminal has a cipher circuit operable in accordance with the key to decipher the enciphered signals. In a preferred form each cipher circuit is a pseudo-random sequence generator for generating pulses in accordance with the predetermined key and the output of which is connected to one input of a gate, the other gate input being connected to the data signals. By enciphering the signals prior to transmission some pages can be dedicated for the private use of selected viewers to whom the cipher key is available.

REFERENCES:
patent: 3061672 (1962-10-01), Wyle
patent: 3170033 (1965-02-01), Vasseur
patent: 3491199 (1970-01-01), Weinstein
patent: 3493674 (1970-02-01), Houghton
patent: 3519736 (1970-07-01), Dorsey
patent: 3659046 (1972-04-01), Angeleri et al.
patent: 3715478 (1973-02-01), Vasseur
patent: 3984624 (1976-10-01), Waggener
Darrington, "Wireless World Teletext Decoder", Wireless World, Nov. 1973, pp. 498-504.
Edwardson et al., "Ceefax: A Proposed New Broadcasting Service", Journal of SMPTE, vol. 83, Jan. 1974, pp. 14-19.

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