Tape recorder: is a system of recording and reproducing sound which uses a magnetic tape. When the recorder operates the tape runs through a recording head having electro-magnets. Sound waves pass through a microphone connected to the recording head. These sound waves cause the electric currents in the head to vary or fluctuate and thus set up a magnetic pattern. The pattern is impressed on an iron wire or metal-coated tape. When the tape is played back the magnetic pattern produces varying electric currents in the coils of the head. The varying electric currents are amplified and converted into sound waves by the loudspeaker.