High density data storage on audio compact cassette tape using a low-cost tape transport

Abstract

A parallel encode/decode software algorithm has been designed for the recently developed ISS 2/3 code. In addition a low-cost solution has been applied to the problem of tape—head azimuth variation (tape skew). The above enables the recording and playback of direct digital data at 60 kb/s on normal audio compact cassette tape using an 8-track format.The combination of a low-cost tape transport and a standard audio cassette tape produces a high degree of tape skew. This is overcome by encoding control pulses on the outer tracks which are used to introduce the same amount of data skew into the clock signals used to clock the data off the tracks. The self-clocking ISS 2/3 code facilitates clock regeneration which, together with simple de-skew circuitry and software encoding/decoding permits the realization of a low-cost bulk storage system. An increase in the data rate to 1 00 kb/s is possible through the use of equalization and by incorporating data onto the outer, de-skew tracks.