A number of the more commonly known magnetic core access switches are combined in a single analytical model. In addition to yielding as special cases the known access switches on which it is based, this model produces many apparently new switches. Relationships among the various parameters in this model are developed in such a way that the designer may choose the number of drivers, the load-sharing factor, the number of turns of wire per switch core and the magnitude of the maximum disturbing magnetomotive force within certain limits. Several methods are developed for economizing on the number of drivers used in switches, and certain special access switches are treated. The current knowledge is reviewed on a fairly recent and important class of access switches, known as load-sharing zero-noise switches. These switches are compared with one another, and a fundamental theorem is proved that such switches can have no more outputs than inputs. Several new classes of load-sharing zero-noise switches are developed and analyzed; in particular, switches are developed which allow more flexibility in the choice of the load-sharing factor than formerly was the case.

The past decade has been a productive period for development in the field of large-scale digital computers. Magnetics has played an increasingly important part in these developments [1]-[8]. Magnetic cores, tapes, and drums have found almost universal acceptance for memory functions. Some future computers will undoubtedly use magnetic logic and control circuits. This survey is a capsule view of twenty-four square-loop magnetic logic circuits which have been proposed or developed so far, with a brief description of the way each circuit or circuit family meets the requirements of logic circuitry. All circuits are treated with a consistent terminology, and the generic relationships among circuits are stressed. Included in this survey are parallel and series transfer core-diode schemes, core-transistor schemes, and all-magnetic schemes of various topologies.