1002 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



equipment numbers (network location) and directory numbers are 

 required to direct incoming calls to the proper terminals (such as the 

 number group frame in No. 5 crossbar, Fig. 12) and to provide on 

 originating calls information for charging purposes (such as the AMA 

 "Dimond" ring translator,!^ pig 13) Each of these translators for a 

 10,000 line office represent about 10^ bits of information. Another use 

 for passive memory is to translate central office codes into routing in- 

 formation. In local central offices this is also done by cross-connections 

 as shown in Fig. 14. 



Another form of passive memory is the punched card or tape. These 

 have been used widely in telephone accounting systems. A step toward 

 electronic memory is the card translator which provides routing in- 

 formation in the crossbar toll switching system^^ (see Fig. 15). Here the 

 cards represent passive memory and are selected and read by a com- 

 bination of electromechanical action and light beam sensing with 

 phototransistor detectors. One such device equipped with 1,000 cards 

 represents the storage of approximately 10^ bits of information. 



In all of the above types of passive memory limitations in the speed 

 are involved in the choice of devices used within the memory or the 

 access to it. This is one of the reaons these translators are subdivided so 

 that the various portions may be used in parallel in order to satisfy the 

 total information processing needs of the office. 



A discussion of passive memory would not be complete without one 

 further illustration, Fig. 16. This is a wiring side view of a typical relay 

 circuit in the information processing portion of a switching system. It 



o- 



EN 



SWITCHING 



NETWORK 



A| 



MARKER 

 A2-P1 



DN-^EN 

 P2 



REGISTER 



A = ACTIVE MEMORY 

 P = PASSIVE MEMORY 



ON 



Fig. 11 — Memory in typical electromechanical switching system. 



