METHOD AND APPARATUS FOR DELIVERING SECURED TELEPHONY SERVICE IN A HYBRID COAXIAL CABLE NETWORK

摘要

A hybrid coaxial cable network employs interdiction to ensure privacy in telephony communications. Video and telephony signals are secured such that telephony and interactive video signals to and from a subscriber do not appear on the network at any other subscriber location. Combined video and telephony signals transmitted from a control office 13 over a network including fibre optic and coaxial cable transmission systems are supplied to subscribers via a selective delivery arrangement 37 including an interdiction device 16, and modulator/demodulator 39 and a power supply unit 41. In interdiction device, 16, a jamming oscillator or a negative trap circuit 49 is provided to pass video signals and to interdict all downstream telephony signals. An isolation amplifier 47 and forward coupler 48 passes interactive video signals but block telephony signals. Modulator/demodulator 39 ensures that only selected telephony channels are delivered to and from a subscriber.