The assessment of the reliability of magnetic tape for data processing

A large number of specimens of tape have been tested for drop-outs over a wide range of operating conditions. All specimens showed the same characteristic behaviour and lead to the conclusion that there is a drop-out distribution which is inherent in the structure of tape and independent of any foreign particles or mechanical damage introduced in the manufacturing process or subsequent handling. The observed distribution permits of simple mathematical expression in terms of two of the major variables of operation, drop-out discrimination level and pulse packing density. A simple theory of the origin of the observed behaviour is given, and a method of tape testing is suggested which appears to be more basic than the present ¿go/no-go¿ type of test. The method permits batch testing for most purposes and saves valuable time in the selection of suitable tape even if complete testing if insisted upon. It also gives information which should be useful in the design of systems to handle tape and in the calculation of the improvement of reliability resulting from methods of introducing redundancy into the storage system.