Key finder

The Key Finder is attached as a key ring on the key. To recover a lost key, suffices a sudden loud noise such as whistling or - in some models - hands clapping. The key finder is, if it is located in the vicinity of the sound, as an "answer " a series of beep tones. Hearing thus allows finding the key, in particular if the searched object is covered by another. Some models are also equipped with an LED or other light source and also give an optical signal by itself.

The range is specified with five to ten meters. The key finder is usually a flat cuboid with a few centimeters edge length that fits in your pocket. To operate a battery ( a button cell in the rule) is necessary. The key finder is since the late 1980s on the market and is often offered as a giveaway.

Some key finder not only respond to whistles, but also to other similar sounds, such as music or a ringing phone.

• Household appliance