Resources Contact Us Home
Coding system for pay television apparatus

Image Number 5 for United States Patent #4025948.

At the sending end, a plurality of high-frequency oscillators each furnish a signal having a frequency different from the frequency of the other of the oscillators. Timing signals derived from the television signal and signals from a random pulse generator are combined to furnish enabling signals for enabling the high-frequency oscillators during predetermined time intervals of the television signal and in a random order. A logic circuit which includes externally operable switches for setting up a program code assignment receives the enabling 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 in the television signal. A mixer mixes the oscillator signals into the encoded television signal. At the decoder the oscillator signals are filtered out, and a logic circuit set up in accordance with a punch card having a program corresponding to the code assignment at the encoder furnishes a decoder control signal which causes a reversal of the polarity of the picture signals thereby reestablishing a standard television signal.

  Recently Added Patents
Electromagnetic sensor cable and electrical configuration therefor
Clock phase recovery apparatus
Packaging article
Enabling improvement in cellular network coverage
Antenna device and wireless communication apparatus
Event-associating software application for accessing digital media
Position pointer, variable capacitor and inputting apparatus
  Randomly Featured Patents
Downhole mixing valve
Topical ophthalmic compositions containing microfine retinoid particles
Method and apparatus for player communication
Precursor electrical pulses to improve inkjet decel
Apparatus including an error detector and a limiter for decoding an adaptive differential pulse code modulation receiving signal
Multiplier for binary numbers in two's-complement notation
Contaminant-reactive gabion and method of manufacture and use
Antistatic stabilizer and final wash additive for photo developing
Theft preventing device, particularly for bottles
Waste water treatment tank