590 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



improvements in reliability, increase in speed, and, most important of all, 

 reduction in cost. Operable arrangements to meet all sorts of conditions of 

 use can generally be selected from the present fund of knowledge but the 

 choice in practice is much more limited than in theory. However, translators 

 and identifiers, particularly those used on a large scale, can be varied in 

 many ways to obtain maximum usefulness and to minimize the costs, not 

 only of these devices themselves, but also of other parts of the associated 

 system. 



In the following discussion a number of devices of these types will be 

 illustrated to provide a general review of some of the methods available, 

 and the factors encountered in practice in trying to obtain a proper balance 

 between costs and usefulness will be examined. 



Translators 

 What are Translators? 



The translators with which we are concerned in this discussion deal only 

 with information in the form of electrically coded numbers. The "languages" 

 carrying this information are the coding systems made up of the numbering 

 bases and signalling methods. Unfortunately, the analogy between the switch- 

 ing system translator and an interpreter of languages, implied by our use of 

 the word ''translator," is not very consistent. 



The term ''translator," as used in this paper, means broadly a switching 

 system element which, in response to an inquiry in the form of an input code, 

 suppHes an answer in the form of an output code to the element presenting 

 the input code or to some other element. Each code may represent one or 

 more numbers. 



The translator may be a device which serves a number of other circuit 

 elements in common, or it may be associated with a single such element or 

 even built into it and unnamed. 



Now in practice we will find that in some applications translators are used 

 so that the input codes and corresponding output codes represent the same 

 numbers in different bases or with different signalling methods, that is, the 

 same information in different languages. Here we have the nearest approach 

 to our implied analogy. However, quite commonly, the switching translator 

 is required to do things which would be decidedly out of order in the case 

 of language translation, such as changing the information instead of the 

 language or changing both at the same time. 



Some of the variations in switching translator applications which should 

 be noted at this point are: 



(1) In practice, translators are arranged with a multiplicity of input and 

 output possibilities. The inputs may be permanently associated with 



