Jack Wyatt, age 12, of Billings, Mont., for his question:
WHEN WERE TAPE RECORDERS FIRST USED?
A tape recorder is a device for recording sound, pictures and various kinds of information on magnetic tape. The first machine used for recording sound magnetically was invented in the late 1800s by Danish engineer Valdemar Poulsen.
Poulsen's machine made a magnetic recording on steel wire. It didn't prove to be popular and very little use was made of magnetic recording for many years.
In the 1930s, German engineers found a more efficient and convenient substitute for the steel wire used in Poulsen's recorder. They worked out a method for using plastic tape coated with a magnetic material.
During World War II, the Germans further developed the process of recording on magnetic tape. And after the war, engineers in the United States went to work on the project.
By the 1950s, tape had largely replaced phonograph records for most radio recordings. Stereo tape recorders were introduced in the U.S. and Canada in 1955. About the same time, television networks started to record programs on videotape.
During the early 1960s, many radio stations started to use cartridge tape recorders for broadcasting music. Cartridge recordings were mass produced for the first time in 1965, as optional equipment for a number of 1966 model automobiles.
Scientists in The Netherlands developed the cassette audio tape recorder in the early 1960s. Cassettes were then introduced in the U.S. in 1964 and almost immediately this type of cassette became the most popular type of audio tape recorder. Cassette videotape recorders were developed in the late 1960s.
Also, in the late 1960s, American physicist Ray Dolby developed an electronic system that was designed to improve the quality of audio tape recordings. The Dolby system nearly eliminates the faint hissing sound made by other tapes.
The thin plastic magnetic tape on which records are made is coated on one side with particles of iron oxide or some other substance that is easily magnetized. When electronic waves are fed into a tape recorder, they magnetize the particles on the tape in various patterns.
The electric waves may come from a microphone, a television camera or a computer. In fact, anything that can be changed into electronic waves, such as sound is by a microphone, can be recorded on magnetic tape.
When the tape is played back, the magnetic patterns produce electronic signals that are changed back into sounds, pictures or information.
Tape recorders have many uses. They provide home entertainment and are used by the radio, recording and TV industries. Scientists obtain information from tape recordings made on space flights. The uses of tape recorders in business and industry range from recording dictation to storing computer information.