ELECTRONICS IN TELEPHONE SWITCHING SYSTEMS 



1003 



Fig. 12 — No. 5 number group. 



could be any other unit, for example, a trunk circuit. The principal 

 point is that each wire on such a unit is remembering some passive 

 f| relationship between the active portions of the circuit, such as relays. 

 This is the memory of the contact and coil interrelationships as con- 

 ceived by the designer and based on the requirements of what the cir- 

 cuit is required to accomplish. It is the program of what the central 

 office must do at each step of every type of call. Modern digital com- 

 puters have been built with the ability to store programs in bulk 

 memories for the solutions of the various types of problems put to them. 

 It is conceivable that the program of a telephone contral office may also 

 I >e stored in bulk memories to eliminate the need for much of the fixed 

 wiring such as appears in relay call processing circuits. 



