TRANSLATORS AND XDENTIFIERS IN SWITCHING SYSTEMS 617 



limited in function or distinct as a switching unit to be so labeled. Un-named 

 identifiers and identification processes have existed since the early days of 

 the switching art. Only patent attorneys recognized these early arrange- 

 ments and called them by their proper names. 



Let us confine ourselves, for the moment, to the type of device generally 

 named as an identifier. This is a device for indicating in code form the 

 designation of a line, station, trunk, frame or other unit to which the de- 

 vice has a connection. The connection is generally electrical, but could con- 

 ceivably be physical, optical or electro-magnetic. 



Examples of Use 



The term identifier first came into general prominence in connection with 

 the introduction of "automatic ticketing" in the United States and Europe. 

 These are systems used in connection with subscriber dialed toll calls for 

 printing automatically a ticket carrying calling and called numbers and 

 other details necessary to charge for the call. The identifier is the automatic 

 device for determining the caUing number, a function ordinarily performed 

 in manual service by the operator asking for the number. With the identi- 

 fier it is also possible, on those calls requiring the service of an operator, 

 to display the calling number automatically so that the operator's request 

 can be avoided. 



Another example is found in Bell Crossbar Offices of the toll type in which 

 it is necessary for certain equipment to determine the number of the frame 

 on which a calling trunk is located. For this purpose, what is known as a 

 "frame" identifier, is used. 



Of course, no arrangement for fully automatic completion of long haul toll 

 calls can be successful without an automatic system for making a record of 

 the details necessary to charge for the calls, including automatic identifica- 

 tion of the calling number. Identification processes will, therefore, become 

 more and more important. 



Typical Identifiers 

 General 



Existing identifiers follow a number of basic concepts but many varia- 

 tions of these fundamental notions are possible. A few examples illustrating 

 the different concepts with some of their variations will be given. The task 

 is simplified because some of these concepts have a strong resemblance to 

 translator principles which have already been discussed. 



