CENTRALIZED AUTOMATIC MESSAGE ACCOUNTING SYSTEM 1333 



required. This system permits individual and two party customers in 

 No. 1 and No. 5 crossbar offices to dial calls to telephones in their home 

 area. In addition, customers in some No. 5 crossbar central offices may 

 now dial directly to other areas. These facilities have been installed in 

 No. 5 crossbar offices in Englewood, N. J., and in several other locations 

 whose customers now may dial directly to about 13 million telephones in 

 13 metropolitan areas. 



Relatively expensive recording eciuipment is reciuired in each central 

 office in the local AMA system. For new central offices this recording 

 equipment is economical only if the toll and message unit calling rates 

 are relatively high. The addition of local AMA recording ecjuipment to 

 existing offices is, in most cases, uneconomical. 



CENTRALIZED AUTOMATIC MESSAGE ACCOUNTING 



The Centralized Automatic Message Accounting system (CAMA) pro- 

 vides an economical means of recording billing data for customer dialed 

 calls from many central offices that cannot justify local AMA. This 

 sj^stem is economical because one group of recording equipment, located 

 at a crossbar tandem office, can serve as many as 200 local central 

 offices without requiring major changes in, or additions to, those offices. 



The first crossbar tandem equipment arranged for CAMA was placed 

 in service in Washington, D. C, in November, 1953. This equipment 

 serves the customers in 85 central offices in Washington and in suburban 

 Virginia and Maryland. They are able to dial each other directly and to 

 dial their own calls to Baltimore and to other nearby toll points. Even- 

 tually, they will be able to dial their own calls to most points in the 

 United States and Canada. Similar crossbar tandem CAMA equipments 

 have been installed in Detroit, New York, San Francisco and Phila- 

 delphia. 



The CAMA installation at Detroit enables the customers served by 

 approximately 800,000 telephones in 99 Detroit panel and No. 1 crossbar 

 local central offices to dial station-to-station multi-unit interzone and 

 toll calls to 63 communities in Michigan and in nearby Canada. The 

 map of Fig. 1 shows this dialing area. 



THE CROSSBAR TANDEM SYSTEM 



The crossbar tandem system into which CAIMA has been introduced 

 is used today in panel-crossbar and step-by-step areas. It receives calls 

 from local dial central offices and completes them to other local central 

 offices and to the toll network. It is also arranged to receive calls over 



