1014 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



(•omnioii medium bulk memory, fewer system elements are required 

 which ill the overall result in material space saving. 



Another phase of the equipment aspects of electronic switching is that 

 the devices reciuire closer environmental control. Air conditioning 

 appears necessary in early systems because of temperature limitations 

 and other characteristics of some of the devices presently available. 

 Also, vacuum tubes and other high power devices may develop objec- 

 tionable hot spots in the equipment which make it advisable to exhaust 

 hot air. 



MAINTENANCE CONCEPTS 



There is insufficient experience at this time to say what the main- 

 tenance problems of electronic telephone systems will be. Much has 

 been written about the problems encountered in maintaining electronic 



A- 

 B- 



AB+CD=E 

 A LOGIC FUNCTION 



f^T 



WITH RELAYS 



Fig. 25 — A logic function with relays. 



