Abstract: A billing system for use in a chargeable program broadcasting is capable of reliably billing a subscriber for program reception while preventing unauthorized reception thereof. A receiving terminal includes a primary terminal 100 and a secondary terminal 150. The primary terminal 100 receives a compressed video signal and confirms by an error checker 113 thereof whether there is a transmission error and bills, by a billing device 114 thereof, the receiving subscriber on the basis of an error information and a program information, etc., separated from the video signal by a separation circuit 112. The compressed video data is time-axis multiplexed with a terminal identifying code and a key signal and transmitted to the secondary terminal 150. In the secondary terminal 150, a bill for the subscriber is confirmed by the terminal identifying code and the compressed data is decoded by a decoder circuit 166 thereof.

Abstract: In accordance with the present invention, a cable system allows bidirectional digital communication between a plurality of subscriber Digital Video Home Terminals each located at a different subscriber location and a cable headend via a RF Trunk. The cable headend has a processor for calculating and storing a randomized back-off array for each of the plurality of subscriber Digital Video Home Terminals. Each subscriber Digital Video Home Terminal receives the randomized back-off array for controlling through an algorithm when a Digital Video Home Terminal attempts to send a message to a cable headend. If a collision between the two messages is imminent, the last Digital Video Home Terminal to send the message backs-off and then reattempts to send the message a plurality of times after a random back-off interval of time has passed after each reattempt until no collision would occur with another message generated from a different Digital Video Home Terminal.