An analysis of magnetic recording

MAGNETIC recording is the process of transforming electric impulses, varying with time, from an electric circuit to a succession of fixed magnetic fields, varying with distance, along a filament of ferromagnetic material. The magnetic-field space variations are closely proportional to the time variation of the original electric impulses for good recording. The transformation of electric impulses to variations in magnetic field along a wire or tape is accomplished by passing the ferromagnetic wire or tape across an air gap in the iron core of an electromagnet energized by current impulses passing through the coil of the electromagnet. Passing the magnetized wire or tape across the air gap of a similar electromagnet causes a voltage to appear across the terminals of the coil of this second electromagnet. The first electromagnet, used for impressing the electric impulses upon the magnetic recording medium, is called the recording head. The second electromagnet referred to, used for retranslating the stored magnetic impulses into electric impulses, is called the playback head.