초록 ▼

A high security subscription television system which includes the feature of dynamic scrambling and descrambling of cable-connected television signals in response to real-time coded control signals. The system also has the ability to precisely tune the frequency converter unit at the subscriber\s si

A high security subscription television system which includes the feature of dynamic scrambling and descrambling of cable-connected television signals in response to real-time coded control signals. The system also has the ability to precisely tune the frequency converter unit at the subscriber\s site, in response to real time coded control signals provided by a computer at the central transmitting station. Various methods of scrambling and descrambling are described which use manipulation of the video signals at the baseband video level, and also at the RF level. Alternate embodiments of the descramblers include a secondary source for the reference carrier signal required for proper descrambler operation. In an ultra-stable embodiment of a subscriber\s control terminal, a single crystal controlled master oscillator is used to control the frequency conversion unit, to provide a clean reference carrier signal for the descrambler unit, and to tune the control signal receiver, thereby removing the need for frequent fine tuning control adjustments, and further allowing simplified system design and fabrication.

대표청구항 ▼

A method of operating a subscription television system, comprising the steps of: I. At a central transmitting station: (a) generating a standard television signal having a video signal component with predetermined amplitude and polarity relationships; (b) scrambling and amplitude modulating successi

A method of operating a subscription television system, comprising the steps of: I. At a central transmitting station: (a) generating a standard television signal having a video signal component with predetermined amplitude and polarity relationships; (b) scrambling and amplitude modulating successive fields of the standard television signal in a time-coded way so as to provide a complete scrambled amplitude modulated television signal which has said predetermined polarity reversed for at least some fields thereof, and which is amplitude modulated on a channel carrier having a first frequency in the CATV channel assignments; (c) generating a coded control signal stream having first portions containing respective subscriber addresses, second portions identifying the channel carrier frequency, and third portions containing scrambling signals which identify the polarity of each field of the complete scrambled television signal; (d) modulating the coded control signal stream on a code carrier having a second frequency different from said first frequency, in the CATV channel assignments; and (e) transmitting the complete scrambled television signal and the modulated coded control signal stream to at least one subscriber control unit.