V-chip

thumb|U.S. President Bill Clinton holding a [[printed circuit board containing a prototype V-chip module in 1996]] V-chip is a technology used in television set receivers in Canada, Mexico, Brazil, and the United States, that allows the blocking of programs based on their ratings category. It is intended for use by parents to manage their children's television viewing based on blocking systems. Televisions manufactured for the United States market since January 2000 are required to have the V-chip technology. Since the idea for blocking programs in this way was patented and tested in Canada by Brett West and John P. Gardner in 1994, the device remains in use into the age of digital television, however it only blocks programming from standard cable and broadcast television and does not block news, sportscasting, movies on premium cable channels, or streamed programs via the internet.

Analog V-chip technology works much like closed captioning and uses the vertical blanking interval in the television signal. The system receives a special code in the broadcast signal that indicates the show's score according to a simple numerical rating system for violence, sex, and language. The programs' signals are encoded based on their rating, on line 21 of the broadcast signal's vertical blanking interval using the XDS protocol, and this is detected by the television set's V-chip. If the program rating is outside the level configured as acceptable on that particular television, the program will be blocked. The V-chip does not block infomercial, news or sportscasts, which are unrated.