Ternary 3PM magnetic recording code and system

In 1976, ISS Sperry/UNIVAC introduced the 8434 disk drive with the binary 3PM code. This code increased the linear bit density by 50% over the generally accepted MFM code. The present paper introduces the ternary version of the 3PM code that is capable of further increase in bit density. This new code uses ternary signal elements, still relying on saturation recording techniques. The ternary alphabet permits the use of more combinations than the binary. Therefore, higher code rate (2/3) and Targer detection window (66%) can be realized than in binary. Test results show 6,000 bits/cm linear bit density on 3370 equivalent head/disk interface with an error rate better than 1 × 10^-10.