600 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



a switching control code. Note the similarity of the operation to that of 

 the preceding translator. 



The 3-digit decimal input code is first translated by the systematic 

 relay tree to a one-out-of-one-thousand code. The marked code point is 

 cross-connected to an arbitrary route relay, the contacts of which are in 

 turn cross-connected as necessary to arbitrary code marking leads to 

 provide the required information to the control equipment. 



Depending on the economic factors determined by the holding times of 

 the translators and elements served by them and the size of the translator, 

 this type of translator may be individual to such elements or be arranged 

 in common groups. 



Preliminary Resume 

 Systematic Translators 



On the basis of the illustrations given so far, it is possible to make a few 

 observations which will help in the discussion of the more advanced types 

 of translators to follow. 



In the first place, it will be evident that the systematic translators used 

 as examples follow no common pattern. Each design has been carefully 

 tailored to minimize the cost by taking full advantage of the particular 

 relationship between the input and output codes. 



This applies not only to the three varieties previously illustrated but also 

 to numerous other forms used in practice. Among these may be mentioned 

 systematic translators having the general functions of the one shown in 

 Fig. 1, but dealing with the different numbering arrangements found in 

 some common control systems outside of the Bell System. 



Others are those used for translating code marking lead systems from a 

 base of 1-out-of-lO to 2-out-of-5, 3-out-of-8 to l-out-of-40, combinations of 

 4 to 1-out-of-lO or vice versa, etc. Translations between binary and decimal 

 numeration also occur. These changes in the method of indicating a number 

 within the same switching equipment are, of course, not due to engineers 

 merely changing their minds, but are necessitated by the fact that, no 

 matter what system of numeration and coding may be used within a switch- 

 ing system for the sake of efficiency, telephone numbers and charges for 

 calls must be presented in generally understood terms in so far as the 

 subscribers are concerned. 



All of the above fixed translators involve rather simple relationships 

 between the input and output codes. The rules for determining the output 

 codes are in reality instructions for arithmetical treatment of the input 

 code, but the translator does this in a special way without recourse to true 

 computing processes. 



