What is "clap-o-meter"

A clap-o-meter, clapometer or applause meter is a measurement instrument that purports to measure and display the volume of clapping or applause made by an audience. It can be used to indicate the popularity of contestants and decide the result of competitions based on audience popularity. Specific implementations may or may not be based on an actual sound level meters. Clap-o-meters were a popular element in talent shows and television game shows in the 1950s and 1960s, most notably Opportunity Knocks, but have been since been supplanted by other, more sophisticated, methods of measuring audience response.