TRANSLATORS AND IDENTIFIERS IN SWITCHING SYSTEMS 613 



Detailed Considerations 



It has already been brought out that large scale changeable translators 

 known to the present art follow the same basic concept and that there are, 

 as a result, certain problems common to all of them. 



Let us examine Fig. 10 to see how some elements can be varied to change 

 costs. This figure shows four general arrangements for coding, all working 

 into the same output code marking lead bus-bar system. In practice all 

 of the coding elements of the same translator would be of the same form and 

 a large number would appear before the bus system or sections of the bus 

 system. In the general arrangement covered here the coding elements are 

 arranged in numerical order each permanently connected to its associated 

 output bus bars. Types of systems having no output bus-bar multiple, 

 such as the Dimond ring, slide bar or card translators are not illustrated, 

 but covered in the discussion. 



Starting at the left with the input code leads, we have theoretically 

 much choice as to the types of signaling (various combinational or sequen- 

 tial t3rpes) and the system of numeration making up the input code. In 

 spite of this freedom most translators in use employ decimal inputs with 

 signaling generally on a code marking lead basis or sometimes on a decimal 

 pulsing basis. Where code marking lead signaling is used the marks are 

 almost always simple off-on marks and, for decimal notation, each place 

 is represented by a 1 out of 10, 2 out of 5 or combinations of 4 group. The 

 practical choice is limited by the fact that it has usually been uneconomical 

 to change the coding system of the translator input to other than that 

 existing at the output end of the relay or switch devices making use of the 

 translator, as this would require a change of language by intermediate 

 translation. 



If it were not for these limitations the number of input leads could be 

 reduced by use of binary numeration for marking leads, or by signaUng 

 over a single pair of wires with any of the other well known methods of 

 signaling. However, the reduction of leads could, in any case, effect only 

 minor savings as the leads are short. The largest savings possible would be 

 in the reduction of the amount of translator selecting equipment required. 



The language of the translator input, of course, also affects the design 

 of the coding element selector which could be any type of selecting equip- 

 ment such as switches, relays, tubes or code-bar mechanisms or, in one 

 proposal, self-selecting coding elements. Relay trees are frequently used and 

 optimum designs for the common types of inputs are well estabUshed. For 

 different types of inputs the design of such trees profits by mathematical 

 analysis. 



