Pay television system utilizing multi-frequency passive filters

Claim 1

Pay-per-view television system for viewing units, comprising in combination, means for generating a program signal throughout each viewing unit, means for generating at least a first, second, and third interference signal, having respectively a first, second, and third frequency, means connected to said interference signal generating means and to said program signal generating means for injecting at least a selected two of said interference signals simultaneously into said program signal, thereby creating a coded signal, means for transmitting said coded signal to a plurality of subscriber locations, and filter means, including at least a two frequency trap constructed with discrete components, said two frequency trap having an input terminal connected to receive said coded television signal, an output terminal adapted to be connected to a selected viewing unit for filtering said selected two interference signals from said transmitted coded signal, a multiplicity of transformers, each having a tuned secondary and a primary winding, and means for connecting said primary windings in series between said input terminal and said output terminal, whereby said program signal is restored.