Abstracts of Technical Articles by Bell System Authors 



A Sampling Inspection Plan for Continuous Production} H. F. Dodge. 

 This paper presents a plan of sampling inspection for a product consisting 

 of individual units (parts, sub-assemblies, finished articles, etc.) manufac- 

 tured in quantity by an essentially continuous process. 



The plan, applicable only to characteristics subject to non-destructive 

 inspection on a Go-XoGo basis, is intended primarily for use in process 

 inspection of parts or final inspection of finished articles within a manufac- 

 turing plant, where it is desired to have assurance that the percentage of 

 defecti\'e units in accepted product will be held down to some prescribed low 

 figure. It differs from others which have been published in that it pre- 

 sumes a continuous flow of consecutive articles or consecutive lots of articles 

 offered to the inspector for acceptance in the order of their production. It 

 is accordingly of particular interest for products manufactured by con- 

 veyor or other straight line continuous processes. 



In operation, the plan provides a corrective inspection, ser\-ing as a partial 

 screen for defective units. Normally, a chosen percentage or fraction / of 

 the units are inspected, but wlien a defective unit is disclosed by the in- 

 spection it is required that an additional number of units be inspected, the 

 additional number depending on how many more defective units are found. 

 The result of such inspections is to remove some of the defective units, and 

 the poorer the qualit}- submitted to the inspector, as measured in terms of 

 per cent defective, the greater will be the corrective or screening effect. The 

 object of the plan is the same as that incorporated in some of the sampling 

 tables already published, namely, to establish a limiting value of "average 

 outgoing qualit}'" expressed in per cent defective which will not be exceeded 

 no matter what quality is submitted to the inspector. This limiting value 

 of per cent defective is termed the "average outgoing quality limit (AOQL)." 



The theoretical solution treats the case of inspecting a continuous flow of 

 individual units and is based on the distribution of random-order spacing of 

 defective units in product whose quality is statistically controlled. Part III 

 of the paper extends the application of the method to a continuous flow of 

 individual lots or sub-lots of articles. 



Stability in High-Freqiiency Oscillators." R. A. Heising. This paper 

 discusses frequency stability with change in plate voltage of high-frequency 



^ The Annals of Mathematical Statistics, September 1945. 

 ^Proc. I.R.E., November 1943. 



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