04712238 is referenced by 230 patents and cites 31 patents.

A system in a subscriber television network for enabling descrambling of a received scrambled signal on a prepaid basis and/or an impulse-purchase basis. A received mask signal uniquely related to the scrambled signal is compared with a received authorization signal indicating whether the subscriber is authorized to receive the scrambled signal on a prepaid basis and a prepaid signal for enabling descrambling is provided when the compared signals match. A not-prepaid signal is provided when they do not match. A received cost signal indicating the charge for descrambling the scrambled signal and a received credit signal indicating only the subscriber's accumulated credit are processed with reference to a stored record of the subscriber's prior accumulated charges to determine whether the subscriber has sufficient available credit to pay for descrambling of the scrambled signal. If a program is not prepaid and if sufficient credit is available, the subscriber is given the option of causing the signal to be descrambled on an impulse-purchase basis. To prevent a subscriber from obtaining descrambling through such deceit as changing the mask, authorization, cost and/or credit signals, these signals are processed with key signals which are used in scrambling and descrambling the television signal such that descrambling is prevented if any of the mask authorization, cost and/or credit signals is changed.

Title
Selective-subscription descrambling
Application Number
6/618917
Publication Number
4712238
Application Date
June 8, 1984
Publication Date
December 8, 1987
Inventor
Robert D Blakeney II
Del Mar
CA, US
Michael Van Harding
San Diego
CA, US
Jerrold A Heller
San Diego
CA, US
Klein S Gilhousen
San Diego
CA, US
Agent
Edward W Callan
Assignee
Cable Home Communication
CA, US
M A COM Government Systems
CA, US
IPC
H04L 9/00
H04N 7/00
H04N 7/167
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