TRANSLATORS AND IDENTIFIERS IN SWITCHING SYSTEMS 589 



The advent of the process which made the dial an order-passing device 

 rather than a direct-control device, of course changed the entire conception 

 of what could be used in the way of automatic switches, how they were 

 controlled and the number and arrangement of switching paths. But more 

 important than the effect on technical methods in the equipment was the 

 fact that the principle of translation reduced the limitations which sub- 

 scriber numbering arrangements formerly had on the economy of giving 

 subscribers direct access, by dialing, to large numbers of central offices in 

 compUcated networks. First the benefit of this was in facilitating dial service 

 in large metropolitan areas, later in making available suitable methods for 

 diaUng of toll calls by subscribers. In other words, the translator was a 

 practical means of pushing back the horizon for automatic telephone 

 service. 



Systems based on the use of the translation principle are now found in 

 many countries, and the Bell System's most modern crossbar arrangements 

 depend on it more then ever. It is difficult to conceive of a nationwide auto- 

 matic toll switching plan for a country as large as the United States without 

 the use of translation. 



Identifiers are not so old as translators and have, so far, influenced the 

 general design of switching systems in only a minor way. Their importance 

 Ues in the fact that they were key elements in introducing to subscribers, 

 both here and in Europe, a new kind of toll service. With this service, when- 

 ever a subscriber dials a toll call, equipment in the central office auto- 

 matically determines his own number and prints or otherwise makes a 

 lecord of it along with other details of the call so that eventually he can 

 receive a complete statement of toll calls which have been dialed and the 

 detailed charges for each. 



Identifiers were essential in the first offices in which this service was pro- 

 vided in order to determine the number of the calling party, and are neces- 

 sary in plans now envisioned for giving this service in the large number of 

 old-type offices still in service in the Bell System. 



Our newer type offices arranged for this service do not employ devices 

 named "identifiers" as the identification function is spread over numerous 

 elements. Nevertheless, the identification process is there and, named or 

 not, it is found in many other situations. 



Translators and identifiers, while used for functions which seem offhand 

 to be quite different, are often similar in so far as the general operation and 

 problems of design are concerned and, in fact, have much in common with 

 numerous circuit elements called by different names. Because of their funda- 

 mental importance they have been the subject of much invention, directed 

 toward use in specific conditions, the use of different types of apparatus, 



