Statistical probability of worst-case patterns in coincident-current ferrite-core stores

In coincident-current ferrite-core stores, there is a particular pattern of stored information associated with any core which gives a large ¿noise signal when that core is read out. Patterns very near to this worst-case pattern also give unwanted ¿noise, and this paper calculates the average frequency with which a particular pattern occurs against its nearness to the complete worst-case pattern. For randomly operated 642planes the complete worst-case pattern occurs very rarely, and hence the large ¿noise associated with it is rarely encountered. However, lower ¿noise voltages from less complete patterns occur significantly often. The mean frequency of occurrence of a particular ¿noise is plotted against its magnitude, expressed as a fraction of full worst-case ¿noise. In 322 and 162planes, complete worst-case patterns occur more frequently. The ¿noise voltages associated with them may be expected to occur significantly often, if the planes are randomly operated. A complete worst pattern may also be disturbed in the worst possible way, creating an `absolute¿ worst-case pattern, which would give the maximum possible ¿noise. This is an extremely rare event, for any of the commonly used plane sizes, and even an incomplete absolute worst-case pattern, with half the cores arranged to give little ¿noise, is still extremely rare for all but 162planes.