Clapping twice would so sound like this: "clap" (half-second pause) "clap" (one and a half second pause). The Clapper includes three "clap detection" LEDs to assist you. A light illuminates whenever a clap is heard. There are two types of claps: single, when you make only one sound; and double, when you make two sounds in succession. The original Clapper was invented by Henry Klassen at Philips Electronics in 1973. It was an instant success, helping to improve sales of television sets all over the world. It's hard to believe but the Clapper is now 40 years old! During that time it has been adopted as a feature on many more televisions sets all over the world. Even today, it's still used by scientists to detect magnetic fields around the earth, due to its low cost and simplicity. However, some modern televisions have moved away from using the clapper mechanism to indicate audio levels, instead relying on digital displays or vibrating motors inside the remote control. These devices can be difficult to use in dark environments or with speakers located far away from the viewer. As well as being used on television sets, the clapper mechanism is found in many other products where there is a need to detect brief sounds.