People meter

The People Meter is a device and system designed by Nielsen Media Research to allow a relatively passive measurement of the viewing habits of TV and cable audiences.

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.