Some reliability aspects of systems design

Elementary principles of probability theory are used and a systematic development is presented which leads to formulas, charts and guide rules for engineers involved in the design of systems and equipments. Examples are given which illustrate the use of the formulas and the principles derived. This study attempts to show that when the problem of obtaining reliable equipment which consists of unreliable parts is present the solution is redundancy. Complexity by itself need not necessarily lead to unreliability if complexity is used correctly. Two very simple redundancy schemes are described and analyzed. It is shown that it is possible to obtain a desired reliability at relatively reasonable cost in terms of increased size and weight.