V-chip

V-chip is a generic term for technology used in television set receivers in the USA, Canada, and Brazil which allows the blocking of programs based on their ratings category. It is intended for use by parents to manage their children's television viewing. Televisions manufactured for the United States market since 1999 and all units as of January 2000 are required to have the V-chip technology. The idea for blocking programs in this way was patented by Brett West and John P. Gardner in 1994 and tested in Canada. Since then many devices using V-chip technology have been produced.


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 which indicates the show's score according to a simple numerical rating system for violence, sex, and language. The programs' signals are encoded according to 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 is blocked. The V-chip does not block news or sports casts as this sort of programming does not have ratings.
   
The V-chip has a four-digit numerical password in order to keep older children from changing its settings. However it can be overridden by anyone who reads the television's manual to find out how to reset the password to 0000 (built into the V-chip in case the parents themselves forget the password that they set).
The phrase "V-chip" was purportedly coined by Representative Edward J. Markey of Massachusetts. According to him the "V" stands for "violence". However, in an interview with Tim Collings, one of the people who claim to have invented the device, he says that it was intended to stand for "viewer control."