The effects of record head saturation on digital output

Digital recording is usually achieved by driving the record-head core material to only 30-40% of its saturation magnetization. Saturation of the core material will occur only when attempting to record on magnetic media of very high coercive force. Magnetic recording materials with coercive forces of 1100, 1800, and 3600 oersteds have been investigated for low-density digital recording on magnetic-stripe cards. Two record heads of identical construction but different core materials, mumetal and a high-saturation-magnetization iron-cobalt alloy, were used for recording 165 flux changes per cm (420 fci). The initiation of pole-tip saturation in both heads was detected by the decrease in inductance. The mumetal head was unable to fully record either the 1800 or 3600-Oe coercive-force materials because of pole-tip saturation. The high-field head recorded all materials.