S4 BELL SYSTEM TECHNICAL JOURNAL 



Manual Positions Required in Machine Switching Offices. While 

 regular calls between two subscribers will be completed in this system 

 without the aid of operators, certain classes of calls, such as toll calls 

 to suburban points and calls for discontinued or changed numbers, 

 etc., will require the assistance of an operator. Special manual posi- 

 tions are therefore provided in the machine switching office for this 

 service. These positions also care for cases where the subscriber 

 may need the assistance of an operator for other reasons than the 

 above, and are in addition to the cordless "B" positions previously 

 described. 



The operators are called "Special Service Operators." The sub- 

 scriber signals them by dialing "Zero," which on the dial is also 

 marked with the word "Operator." The connection then progresses 

 in the same general manner, through the district and office selectors, 

 as for any originating call. An idle trunk appearing on the office 

 selector leading to an answering jack before the special service oper- 

 ator is chosen and the sender released. Should a subscriber in any 

 local service area dial a subscriber in another area, the sender will 

 automatically route the call to a special service operator. 



The special service operator in large areas has before her a number 

 of cord circuits having one end terminating in a cord and plug. She 

 also has upon a keyboard a set of keys similar to those described for 

 the cordless "B" position, except that there are additional strips of 

 keys upon which she can write up an office code. The operator 

 answers the subscriber by inserting one of the plugs in the answering 

 jack and, having ascertained the desires of the subscriber, directs 

 the connection to the proper destination by setting up on her keys the 

 proper numerical code. Senders are furnished for these positions 

 so that, as soon as the information from the keyboard has been regis- 

 tered on the sender, the keys are released and are ready for another call. 



The other end of the special service operators' cord circuit termi- 

 nates in a district selector which, either directly or through other 

 selectors, has access not only to trunks which the subscriber himself 

 might call, but also to trunks leading to more distant offices which he 

 cannot dial directly because they are toll points. 



Tandem Operation. There are about 158 central offices in the area 

 shown on the map, Fig. 3. While it is an essential requirement that 

 any subscriber connected to any of these offices be able to reach any 

 subscriber connected to any other office, it is obvious that to furnish 

 trunks from each office direct to every other office would require 

 a great number of long trunks in small groups carrying a very light 

 load most of the time. 



