An interactive television system for selectively retrieving video images or
teletext pages from a remote transmitter (1). User requests are
communicated to the transmitter through the telephone network (5). The
selected images (e.g. teletext pages) are provided with an image address
(a personal teletext page number) and transmitted through a broadcast
medium (4). A broadcast receiver (6) captures, stores and displays images
having a particular address in a further autonomous manner. In order to
prevent co-viewers from tracing the image address and thus watching
personal information intended for an individual user on their broadcast
receivers (3), the service provider sends a control command (the teletext
"stop" command) to the receiver through the network whenever a new image
has been transmitted. Then, the provider broadcasts a different image
having the same image address. In view of the stop command, the individual
receiver will ignore this "pseudo-image" while this image will.