Radiocontrol
Radiocontrol is the name of a measurement system developed in Switzerland that is used to determine the number of listeners to radio stations. Wristwatches equipped with microphones are used. These record tones for four seconds per minute. The recordings are later transmitted to a data center and compared there with the data from radio stations.
In Switzerland, the surveys are carried out by the Society for Consumer Research. On average, 1012 people use watches every day.