An electric guitar is a guitar that uses a pickup to convert the vibration of its strings into electrical impulses. The most common guitar pickup uses the principle of direct electromagnetic induction. The signal generated by an electric guitar is too weak to drive a loudspeaker, so it is amplified before sending it to a loudspeaker. Since the output of an electric guitar is an electric signal, the signal may easily be altered using electronic circuits to add "color" to the sound. Often the signal is modified using effects such as reverb and distortion.
Electric guitars were originally designed by guitar makers and instrument manufacturers. Some of the earliest electric guitars adapted hollow bodied acoustic instruments and used tungsten pickups. The first electrically amplified guitar was designed in 1931 by George Beauchamp, General Manager at National Guitar Corporation with Paul Barth who was Vice President.The maple body prototype for the one piece cast aluminum "Frying Pan" was built by Harry Watson, factory superintendent of National Guitar Corporation.Commercial production began in late summer of 1932 by the Ro-Pat-In Corporation (Electro-Patent-Instrument Company Los Angeles),a partnership of Beauchamp, Adolph Rickenbacker (originally Rickenbacher), and Paul Barth.By 1934 the company was renamed Rickenbacker Electro Stringed Instrument Company.
The need for the amplified guitar became apparent during the big band era as orchestras increased in size, particularly when guitars had to compete with large brass sections. The first electric guitars used in jazz were hollow archtop acoustic guitar bodies with electromagnetic transducers. By 1932 an electrically amplified guitar was commercially available. Early electric guitar manufacturers include: Rickenbacker (first called Ro-Pat-In) in 1932, Dobro in 1933, National, AudioVox and Volu-tone in 1934, Vega, Epiphone (Electrophone and Electar), and Gibson in 1935 and many others by 1936.