608 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



side to cause the auto selection of the coding tube for (A) number 1925 as 

 follows: 



(1) Breakdown voltage is applied through the thousands register to the 

 # 1 bus in the thousands group of the A side. This causes breakdown, 

 or firing, at the thousands anode of all tubes that have one as the 

 thousands A digit. In a fully equipped system this would be yo of all 

 the tubes, or 1000. 



(2) ''Sustain" or ''hold" voltage (lower than breakdown voltage) is 

 applied to the ^ 9 hundreds bus, followed by removal of the voltage 

 from the thousands bus. This causes all previously fired tubes which 

 have ^ 9 as the hundreds digit to be held ionized by the hundreds 

 anode and the others dropped out, that is yo of the total tubes drop- 

 ped out and yo or 100 held. 



(3) This drop-out process is continued through the tens and units steps 

 so that first ten and finally only one tube (number 1925) is held by 

 the units anode. Auto-selection of the code tube required is now 

 complete and it remains only to read the coding of the B side. 



(4) Reading is accompHshed by applying "hold" or "sustain" voltage to 

 all the bus bars on the B side. This causes anodes connected to this 

 bus system to fire by transfer in only the one tube which is ionized. 

 Thus all B anodes in tube 1925 will be fired and the resultant currents 

 in the associated bus bars (one in each of the 4 "B" groups) are 

 marks which can be read in the electronic reading circuit to register 

 the B output number 5928. 



(5) The translator is dropped by removing all voltages, causing the 

 selected tube to deionize, and the translator is ready for another job. 

 All of this requires only the time of the various breakdown and 

 transfer steps and intermediate deionizing times, totaling less than 

 100 microseconds. 



The advantages of possible cost reduction are obvious especially for 

 large scale applications. The disadvantages, in the form here shown, are: 



(1) The possible hazards resulting from the fact that this is a single 

 common unit with one-at-a-time operation. 



(2) The tractability for general use needs to be improved as it is neces- 

 sary to change all the 4 or 5 required jumpers on one side of a coding 

 element in order to make a translation change. 



(3) The special tubes need to be made in very large quantities in order 

 to obtain the required low price. 



Further work now being done may resolve all these difficulties. 



This translator illustrates some of the variations the designer can consider 



