Patent ID: 7716711

Claim:
A system for allowing the use of a television transmission system having a transmission band for simultaneous transmission of standard television programs and of a multiplicity of requested data to a plurality of subscribers upon request, without affecting the operation of the standard television broadcasting, the system comprises a standard television transmission system comprising a head end unit and at least one hub connected to the head end unit, wherein the at least one hub includes: at least one central processing unit (CPU) for interfacing with a data storage facility for retrieving requested data and for controlling the generation of specifically allocated pairs of frequencies assigned to a subscriber upon request, by generating instruction codes used in accessing a frequency generating unit; a clock frequency unit to serve as a reference to frequency generation sources; a frequency generating unit for generating a reference frequency and a data carrier frequency pairs in accordance with said instruction codes received from the at least one CPU and in conjunction with the clock frequency unit, the reference frequency and data carrier frequency are selected from a set of predetermined frequencies within pre assigned regions of the television transmission band, the carrier frequency is phase-modulated by said requested data; a combiner for superimposing the frequency pairs and associated controls signals onto the transmission band for in parallel downstream transmission of multiple requested data to user data units, the frequency pairs are superimposed at amplitudes below the standard minimum detectable signal, said control signals include information about said frequency pairs.