Interactive television and data transmission system

A method of communicating information within an area served by a broadcast station transmitting on a broadcast station carrier and within a broadcast station frequency band comprising the steps of:

• (a) modulating the information to be communicated by a carrier other than the broadcast station carrier;
• (b) transmitting at least one side band of the modulation of step (a);
• (c) receiving at a remote location a signal containing the carrier of the broadcast station, and the at least one sideband transmitted in step (b);
• (d) demodulating the signal received in step (c) using the carrier of the broadcast station as a reference to recover a signal corresponding to the signal transmitted in step (b), and
• (e) demodulating the signal recovered in step (d) to recover the information to be communicated.

Apparatus for communicating information within an area served by a commercial broadcast station transmitting over the air on a broadcast station carrier and within a broadcast station frequency band comprising:

• modulation means for modulating the information to be communicated by a carrier other than the broadcast station carrier and for providing an output responsive thereto;
• transmitter means coupled to said modulation means for transmitting, from a transmitter other than the broadcast station transmitter, the output of said modulation means;
• a receiver at a remote location with respect to said transmitter means for receiving as a receiver signal a signal containing the carrier transmitted by the broadcast station and the signal transmitted by said transmitter means, said receiver means having;
• a first demodulator for demodulating said receiver signal using the carrier of the broadcast station as a reference to recover a signal corresponding to the signal transmitted by said transmitter means, and;
• a second demodulator coupled to said first demodulator for demodulating the signal recovered by the first demodulator to recover the information to be communicated.

Apparatus for communicating information within an area served by a broadcast station transmitting on a broadcast station carrier and within a broadcast station frequency band comprising:

• modulation means for modulating the information to be communicated by a carrier other than the broadcast station carrier and for providing an output responsive thereto;
• transmitter means coupled to said modulation means for transmitting the output of said modulation means;
• a receiver at a remote location with respect to said transmitter means for receiving as a receiver signal a signal containing the carrier transmitted by the broadcast station and the signal transmitted by said transmitter means, said receiver means having;
• a first demodulator for demodulating said receiver signal using the carrier of the broadcast station as a reference to recover a signal corresponding to the signal transmitted by said transmitter means, and;
• a second demodulator coupled to said first demodulator for demodulating the signal recovered by the first demodulator to recover the information to be communicated.