different geographical regions. In that way, two different users can be assigned the same page number at the same time as long as they do not receive the TV signals from the same source. Another drawback to the technology is the privacy concerns in that many users can see what a user is doing because the interactive pages are received by all viewers. Also, the user usually has to pay for the telephone call to the TV station. Bulletin boards Spanish prisons have banned or deactivate TV sets with teletext capabilities, after finding that the inmates received coded messages from accomplices outside through the bulletin board sections. Legacy and successors While the basic teletext format has remained unchanged in more than 30 years, a number of improvements and additions have been made. Standard electronic program guide (EPGs), like NexTView, are based on teletext, using a compact binary format instead of preformatted text pages. Various other kinds of information are sent over the teletext protocol. For instance, Programme Delivery Control (PDC) signals—used by video recorders for starting/stopping recording at the correct time even during changes in programming—are sent as Teletext packets. A similar, but different, standard Video Programming System is also used for this purpose. Teletext pages may contain special packages allowing VCRs to interpret their contents. This is used in relation to the Video Programming by Teletext (also known as startext) system which allows users to program their videos for recording by simply selecting the program on a teletext page with a listing of programs. Other standards define how special teletext packets may contain information about the name of the channel and the program currently being shown. Internet services Prestel was a British information-retrieval system based on teletext protocols. However, it was essentially a different system, using a modem and the phone system to transmit and receive the data, comparable to systems such as France's Minitel. The modem was asymmetric, with data sent at 75-bit/s, and received at 1200-bit/s. This two-way nature allowed pages to be served on request, in contrast to the TV-based systems' sequential rolling method. It also meant that a limited number of extra services were available such as booking events or train tickets and a limited amount of online banking. A number of teletext services have been syndicated to web viewers, which mimic the look and feel of broadcast teletext. RSS feeds of news and information