Magnetic tape used to record visual images and sound, or the recording itself. There are two types of videotape recorders, the transverse (or quad) and the helical. The transverse unit uses four heads rotating on an axis perpendicular to the direction in which the tape is fed. The transverse format achieves 1,500-in.-per-minute head-to-tape speed, necessary for high picture quality. The helical unit uses tape traveling around a drum in the form of a helix. VCRs use a helical format, known as VHS (Video Home System), consisting of two helical bands and tape 1/2 in. (1 cm) wide.