Interactive home information system

A system for providing a scrambled signal over a cable television system from a television signal source comprising:

• stripper means for removing the sync signal from the source to provide a sync-stripped output signal;
• subcarrier means for maintaining the chroma subcarrier on the sync-stripped output signal at all times including the period of vertical retrace;
• first modulator means for supplying the resultant scrambled signal at a first carrier frequency over the cable system;
• and
• second modulator means for supplying the sync signal stripped by the stripper means at a second carrier frequency over the cable system.

A system, for decoding a composite scrambled television signal that includes a first carrier, at a first frequency, modulated with a sync-stripped video signal with a continuously present chroma subcarrier and a second carrier, at a second frequency, modulated with the stripped sync signal, the system comprising:

• first demodulator means for demodulating the sync-stripped signal at the first frequency and having an output;
• second demodulator means for demodulating the stripped sync signal at the second frequency and having an output;
• and
• combining means for combining the outputs of the first and second demodulator means in such a way as to restore the television signal.

A cable television system permitting interactive television service comprising:

• a cable system having a headend and trunk end feeder cables for providing information service to subscribers;
• service means at the headend for providing a plurality of digitally compressed video signals;
• mux means at the headend for multiplexing the digitally compressed video signals;
• modulator means at the headend for supplying the multiplexed video signals on a radio frequency carrier;
• and
• at least one node located proximately at a feeder, said node including:
• a headend port for communication with the cable headend;
• a feeder port for communication with a plurality of home interface controllers, each home interface controller having a radio frequency input and a data communications link with the feeder port;
• and
• a plurality of feeder server means, each feeder server means in communication with the headend port and the feeder port, for providing one of a plurality of information services depending on a selection input, each information service having at least an information output, each feeder server means including:
• modulator means for providing the information output of a selected service at a selected radio frequency to the feeder port;
• download means for demodulating, demultiplexing and decompressing the multiplexed video signals received at the headend port;
• and
• node control means, in communication with the feeder port, for determining whether a home interface controller is active based on information received over the data communications link, and, in the event the home interface controller is determined to be active, for assigning a feeder server means to it during the time such interface controller is determined to be active.