Pay television system and sending end encoder means

Details Pay television system and sending end encoder means Pay television system and sending end encoder means

H - Electricity

04

N

350/29

H04N 7/16 (2006.01)

Patent

CA 1124385

Abstract of the Disclosure At the sending end, each of a plurality of code signals generators furnishes a signal having a character- istic (e.g. frequency) different from the corresponding characteristic of the other code signals. Timing signals derived from the television signal and signals from a random pulse generator are combined to furnish enabling signals for enabling the code signal generators during predetermined time intervals of the television signal and in random order. A logic circuit which includes externally operable switches for setting up a program code assignment receives the en- abling signals and furnishes an encoder control signal only in response to certain selected enabling signals. The encoder control signal changes the polarity of the picture signals relative to the synchronizing signals. A mixer mixes the code signals into the encoded television signal. At the decoder the code signals are filtered out, and a logic circuit set up in accordance with a program code assignment corresponding to the program code assignment at the encoder furnishes a decoder control signal which causes a reversal of the polar- ity of the picture signals previously inverted by the encoder. A predetermined pattern of the code signals, designed to cause a bistable circuit at the receiver to change state a predetermined number of times if the decoder is in the correct decoding mode, is periodically inserted into the transmitted encoded television signal. A counter counts the number of state changes and, if correct, a validation signal is furnished. The validation signal allows record- ing of the billing charge for the program and transmission of the decoded signal to the television receiver. Transients -1- generated due to unavoidable timing and slope errors in the leading and trailing edges of pulses used to invert the picture signals are removed by clamping the television signal to a predetermined reference level for short time intervals around each desired switching instant. At the decoder, a clamping circuit clamps the television signal to ground potential during the clamping intervals, thereby balancing the DC components of the signal portions. -1'-

276978

Affiliated with

Also associated with

Rating

Pay television system and sending end encoder means does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pay television system and sending end encoder means, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pay television system and sending end encoder means will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFCA-PAI-O-563363