1012 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 

 EQUIPMENT CONCEPTS 



111 what has been said, consideration was given only to the concepts 

 and circuitry of electronic telephone switching systems, but the things 

 which the manufacturer and user come in contact with are the physical 

 or equipment realizations of these concepts. One thing that is outstand- 

 ing about the physical aspects of an electronic system is the large num- 

 ber of small components which are required. Fortunately, most of these 

 components such as resistors, diodes, transistors, condensers, etc., are 

 all of the same physical or similar mechanical design. From the manu- 

 facturer's point of view the problem then is to find the most economical 

 way in which these many devices may be manufactured, assembled and 

 tested, because of the large numbers required in a system. The basic 

 solution appears to be: automatic production. This has led to the con- 

 cept of small packages of components. These packages are the building 

 blocks of a system and contain basic circuits which may be used repeti- 

 tively. The trend in making such packages appears to be the use of 

 printed wiring with automatic means of placing the components on the 

 printed wiring boards. ^^ 



Despite the fact that there are large numbers of these small com- 



10' 

 10^ 



lO' 



m 



V 10' 



h- 



< 



°- 3 



< 10 

 o 



lO' 

 10 



PHOTOGRAPHIC STORE 

 1 



ELECTRO- 

 STATIC 

 - TUBE 

 STORE 



10' 



IR 



1 COORDINATE 



ACCESS 



ARRAY 



MAGNETIC 

 DRUM 



MAGNETIC 

 / TAPE 



/ SINGLE BIT 

 / MEMORY 



J (_L 



_L 



I 10 10' lO' 10* 10* 10* 



CYCLE TIME -MICROSECONDS 



10' 



10' 10' 



Fig. 22 — Memory system capabilities. 



