138 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



Verification involved a complete audit of the inspection records to 

 provide assurance that all process operations were recorded as having 

 been performed satisfactorily, that the prescribed inspections had been 

 made, and that the recorded results indicated that the product met all 

 of the specified requirements. This work was performed by a group of 

 six Inspection Representatives who had considerably experience in all 

 phases of inspection and inspection records. 



As the verification of a particular piece of apparatus proceeded, a 

 verification report was prepared which, when completed, contained the 

 most pertinent inspection data, such as: 



(1) Recorded measurements of electrical parameters. 



(2) Values calculated from measurements to determine conformance. 



(3) Confirmation that all process and inspection operations had been 

 verified. 



(4) Identification (code numbers and serial or lot numbers) of mate- 

 rials and components entering into the product at each stage of manu- 

 facture. 



The verification report usually listed the data for twenty serial num- 

 bers of a particular code of apparatus along with the specified require- 

 ments. Included, also, was a cross-reference to all the inspection data 

 books involved so that the original data could be located easily. These 

 verification reports were prepared for all apparatus up to and including 

 the finally assembled and tested repeaters. 



The following gives an indication of the number of items examined 

 in the verification of one complete repeater: 



Items verified in data books 17 , 593 



Items verified on recorder charts 1 , 142 



Calculations verified 1 , 580 



20,315 

 Number of entries on verification reports 4 , 070 



Verification reports, in addition to presenting the pertinent recorded 

 data, provided a "field" of twenty sets of measurements from which it 

 was easily possible to spot a questionable variation. For example, it was 

 the adopted practice on this project to examine, critically, any charac- 

 teristic of a piece of apparatus, in a universe of twenty, which varied 

 considerably from the rest, despite the fact that it was still within limits. 



While the number of cases turned up in the verification process which 

 have resulted in rejection of product are relatively few, we believe that 

 the added insurance provided, and the psychological value obtained, 

 considerably outweigh the cost. 



