General problems in the use of electron tubes

This paper concerns the general problems connected with the use of electron tubes. We are primarily concerned with obtaining the utmost reliability when vacuum tubes are employed in circuits to perform certain functions in guided missiles. It is first desirable that we define what we mean by "reliability." Unfortunately, each person has his own definition and idea of just what reliability concerns itself with. The following definition has been developed by a committee on reliability set up by the Radio Television Manufacturers Association and probably fits the bill closer than any definition developed up the present time. The definition is: Reliability is a measure of the probability that a device will perform its purpose adequately for the period of time intended under the operating conditions encountered. This definition covers, in reality, almost every conceivable kind of application and it becomes apparent almost immediately that reliability for one type of service may not necessarily constitute reliability for another application at all. This causes much of the confusion which exists in determining reliable operating. conditions for tubes in specific particular applications. This is brought about by the fact that some applications require the tubes to operate for only a relatively short time, say one-half hour; other applications require the equipment to run for twenty-four hours a day for days on end without any operator being within hundreds of miles of the equipment. In this instance, replacements cannot easily be made and therefore the equipment, to be reliable, must operate thousands of hours without any attention.