A pickup is a transducer that captures or senses mechanical vibrations produced by musical instruments, particularly stringed instruments such as the electric guitar, and converts these to an electrical signal that is amplified using an instrument amplifier to produce musical sounds through a loudspeaker in a speaker enclosure. The signal from a pickup can also be recorded directly. The first electrical string instrument with pickups, the "Frying Pan" slide guitar, was created by George Beauchamp and Adolf Rickenbacker around 1931. Most electric guitars and electric basses use magnetic pickups. Acoustic guitars, upright basses and fiddles often use a piezoelectric pickup. Magnetic pickups A typical magnetic pickup is a transducer (specifically a variable reluctance sensor) that consists of one or more permanent magnets (usually alnico or ferrite) wrapped with a coil of several thousand turns of fine enameled copper wire. The magnet creates a magnetic field which is focused by the pickup's pole piece or pieces. The permanent magnet in the pickup magnetizes the guitar string above it. This causes the string to generate a magnetic field which is in alignment with that of the permanent magnet. When the string is plucked, the magnetic field around it moves up and down with the string. This moving magnetic field induces a current in the coil of the pickup as described by Faraday's law of induction. Typical output might be 100–300 millivolts. The pickup is connected with a patch cable to an amplifier, which amplifies the signal to a sufficient magnitude of power to drive a loudspeaker (which might require tens of volts). A pickup can also be connected to recording equipment via a patch cable. The pickup is most often mounted on the body of the instrument, but can be attached to the bridge, neck or pickguard. The pickups vary in power, and they vary in style. Some pickups can be single coil, while other pickups can be double coil humbuckers. The pickup is one of the most important aspects to distinguishing an electric guitar's sound. Most guitar models have a distinction in pickups, which act as a new selling point for guitar companies. Construction Pickups have magnetic polepieces (one or two for each string, with the notable exceptions of rail and lipstick tube pickups), approximately centered on each string. (The standard pickups on the Fender Jazz Bass and Precision Bass have two polepieces per string, to either side of each string.)