CENTRALIZED AUTOMATIC MESSAGE ACCOUNTING SYSTEM 1339 



Fig. 5 — Switchboard. 



tion which tells the transverter whether to perforate a two- or a four-line 

 initial entry. The two-line initial entry used for calls billed on a message 

 unit basis contains only the calling office code and telephone number, the 

 billing index and the trunk identity whose function is discussed later. 

 This information, together with the duration of the call, is sufficient for 

 billing. Four-line entries contain, in addition, the called office code and 

 telephone number. They are used for detail billed toll calls and for those 

 bulk billed calls on which all details of the call are required for record 

 purposes. Fig. 6 shows a simplified schematic of the billing indexer. The 

 calling office code combined with the customer rate class, chooses a par- 

 ticular rate treatment relay. This rate treatment is common to all cus- 



