1342 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1954 



tions, transverters and billing indexers. As in the local AMA system, 

 testing of the recorder features is done by the test unit on the master 

 timer frame. 



The AMA circuits are provided A\-ith many self-checking features 

 which detect trouble while a call is being handled. When a trouble is 

 detected, the AMA circuits connect momentarily to a recording circuit 

 called a "trouble indicator" which lights lamps to indicate how far the 

 call has progressed and which of the common control circuits were used 

 on the call. This information aids the maintenance force in locating the 

 trouble. 



FUTURE DEVELOPMENTS 



As stated earlier, use of Centralized Automatic Message Accounting 

 by panel and crossbar customers will be restricted initially to calls to 

 the home area and one foreign area. The centralized recording will be 

 done initially at crossbar tandem offices with operators identifying the 

 calling telephones. Ultimately, customers served by all types of dial 

 local central offices will be able to dial their own calls — local or nation- 

 wide. Operator identification of individual and two-party lines will be 

 replaced in many cases by automatic identification. The centralized re- 

 cording equipment A\dll be located in various types of tandem and toll 

 offices as determined by the economics of each case. 



CONCLUSION 



The development of Centralized Automatic Message Accounting 

 arrangements is another major step toward nationwide customer dialing 

 from central offices which cannot be economically equipped with local 

 AMA recording equipment. 



REFERENCES 



1. Pilliod, J. J., Fundamental Plans for Toll Telephone Plant, B.ST.J., 31, pp. 



832-850, 1952. 



2. Clark, A. B., and Osborne, H. S., Automatic Switching for Nationwide Tele- 



phone Service, B.S.T.J., 31, pp. 823-831, 1952. 



3. Nunn, W. H., Nationwide Numbering Plan, B.ST.J., 31, pp. 851-859, 1952. 



4. Shipley, F. F., Automatic Toll Switching Systems, B.S.T.J., 31, pp. 860-882, 



1952'. 



5. Friend, O. A., Automatic Ticketing of Telephone Calls, A.I.E.E. Trans., 63, 



pp. 81-88, 1944. 



6. Meszar, J., Fundamentals of the AMA System, A.I.E.E. Trans., 67, Part I, 



pp. 255-269, 1950. 



7. Collis, R. E., Crossbar Tandem System, A.I.E.E. Trans., 69, Part II, pp. 997- 



1004, 1950. 



8. Cahill, H. D., Recording on AMA Tape in Central Offices, Bell Labs. Record, 



29, p. 565, Dec, 1951. 



9. Jordan, W. C, The AMA Timer, Bell Labs. Record, 30, p. 122, March, 1952. 



