PEOPLE METER

The 'People Meter' is a device and system used by Nielsen Media Research in the USA to allow a relatively passive measurement of the viewing habits of TV and cable audiences. The people meter was invented by a British company called Audits of Great Britain, or AGB for short. The successor company to AGB is TNS, which is not only active in media research in the USA, but also across the globe in 32 countries.
At the broadcaster or cable network, a Nielsen Audio/Video encoder is installed. This device imprints special signaling into the video and audio signals of that entity. At the home, a device is installed that allows the panelist and their family to log in and out of a TV set, allowing Nielsen to develop ratings data for that market.