620 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



cross connections (acting as translators) to the sleeve terminals of all the 

 directory numbers associated with the line and the start anodes of the 

 corresponding directory number tubes, firing each of these tubes at the 

 start anodes. Continuous hold voltage (+75) is also placed on one of the 

 hold or "party" buses through the party station register (station identity 

 previously determined). 



When the operating pulse ends, the cessation of current through the start 

 anodes causes all the operated tubes to de-ionize except the one for the 



EQUIPMENT 

 NUMBER 



INTERMEDIATE 

 ^SWITCH STAGES'^N 



X X X- 



SLEEVE— ' 



TRUNK CIRCUIT 



PARTY I 

 REGISTER I 



PARTY BUS BARS (4) 



HOLD OR PARTY 

 /ANODE 



OFFICE (as REQ.) 



THOU (lO) 



HUNDS (10) 



TENS (10) 



UNITS (10) 



/ — START 

 I ANODE 



FILTER - 



V ^ CLASS (as REQ.) 



ELECTRONIC 



READING 



UNIT 





CONTROL 

 UNIT 



"■-CATHODE 

 CONNECTION 



Fig. 12 — All-electronic calling number identifier with multianode tubes as 

 elements. 



Q 



oa D 



U<Q. 



o 



coding 



wanted number which is held, through ionization transfer, by the party 

 anode. The tube for the wanted number has now been selected and the 

 output code is read by the reading circuit by applying hold voltage to each 

 bus of the system, causing all the coding anodes in the wanted number tube, 

 and in only that one to conduct. Current then flows in one bus in each 

 group, including the class of service group, which indicates the digits for 

 the number and class of service, which are registered electroncially in the 

 read unit. The register reading is transferred to the output code marking 

 lead system. 

 This operation requires less than 30 miUiseconds, which means that a 



