606 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



desired to reduce the number of translators required to the uUimate of one, 

 the great speed needed in order to obtain the required capacity indicated 

 the need for full-electronic methods. Because, figuratively, the equipment 

 could refer to the translation system in terms of one number and obtain 

 the associated number as an answer, in either direction, much as in a cross 

 reference card file, the system was called an electronic cross-reference 

 system. It is promising, but not yet practical. 



In this scheme the general concepts of other translators were not avoided 

 but were applied in a different way. For instance the idea of having the 

 input code select a changeable coding element was not avoided. However, 

 the selecting element itself was ehminated, making possible important 

 savings. The select function was combined with the coding function. Each 

 coding element acts as its own selector under control of the input code, say 

 code A, and then supplies the wanted output code, say code B. The opera- 

 tion may be reversed by supplying code B as an input, which results in 

 auto-selection of the same coding element, but this time code A is supplied 

 as an output. 



The general arrangement is shown in Fig. 8. 



The auto-selection and coding element for each associated pair of codes 

 is a special cold cathode tube of the multi-anode type, having ten point 

 anodes and a common cathode. The anodes are symmetrically spaced 

 around the cathode so that each anode to cathode gap has the same charac- 

 teristics. Only eight anodes are used in this illustration. 



Since there is one tube for each pair of associated numbers there will be 

 a total of 10,000 tubes in this case. Four groups of ten numerical bus bars 

 for the A numbers and the same for the B numbers, passing the entire 

 tube field and cross-connectable to the anodes of the tubes, complete the 

 translator proper. The extraneous equipment consists of ''inquiry" and 

 ''answer" sections, each of which may automatically be connected to 

 either the side A or side B bus bar system. The "run-down" element of the 

 "inquiry" section contains electronic pulsing and sequence-control equip- 

 ment for causing the auto-selection and coding operations. 



The operation is very fast, the entire auto-selection and output code 

 reading process involved in each translation being completed in less than a 

 millisecond if all the connecting switching gear is electronic. 



Assuming that an "A" number, say 1925, has been recorded in the 

 register of an inquiry section, that this section has been connected to the 

 bus bar system of the "A" side and the corresponding answer section has 

 been connected to B bus bar system, we are ready to make a translation. 

 The electronic rundown equipment pulses into the bus bar system of the A 



