Abstract: A system for automatically surveying television viewership detects horizontal and vertical synchronization signals and determines the relative phases of these signals with respect to a time base counter in a survey unit. All stations in the viewing area are monitored to determine the relative phases of the broadcast synchronization signals with respect to a time base counter of the monitoring unit. Then, the data are correlated to determine the channels being viewed. Correlation is made by comparing the direction and magnitude of phase shifts of the synchronization signals in the surveyed unit with the data produced by the unit monitoring all stations.