1112 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



device which prints this information and other data required for charging. 

 The tickets can be used for bulk bills as well as detail records since they 

 can be summarized at the accounting center by manual methods for 

 calls on wliich detail information is not required. 



Automatic message accounting is used with crossbar systems both for 

 bulk billing and detailed call records. With this system the data required 

 for charging is perforated on j^aper tape by common central office equip- 

 ment. The arrangement has been described in the technical literature* 

 and will not be further described here. 



Both the ticketing method and automatic message accounting require 

 the collection of a large amount of data and the ability to do a compli- 

 cated job in handling and recording this data. Tliis demands elaborate 

 and expensive equipment which is practical only when provided on a 

 common basis so that it can be called into service for a short time and 

 then restored to the common pool for other calls. 



Direct dial control systems without common controls can only have 

 message registers on the line and therefore can handle notliing but bulk 

 billed calls. Furthermore because of the expense of arrangements for 

 determining multiple unit charge data and for operating the message 

 register more than once on a call, multiple operation of message registers 

 on individual calls is not practical. 



From coin stations in direct dial control systems the customer may 

 dial calls only to offices within the local charge zone. However, in panel 

 and crossbar areas the "coin zone dialing" arrangement is available to 

 permit coin customers to dial beyond the local zone. With this plan calls 

 are routed to a tandem office where completion is delayed until an oper- 

 ator can plug into the trunk to tandem and supervise the collection of the 

 required coins. The amount to be collected is indicated by trunk lamps 

 which appear in a switchboard multiple. Common controls enter into 

 this scheme at the originating office to route the call to tandem and to 

 determine the charge, and at the tandem office so that the digits can be 

 stored while the call is held up prior to collection of the coins. 



TYPES OF PULSING 



Direct dial control systems are restricted to operation with dial pulses 

 and are usually limited to pulsing speeds of about 10 pulses per second 

 and about one digit per second. Dial pulsing has range limitations which 

 can be overcome by the addition of pulse repeaters at appropriate points. 



Common control systems store the digits in senders which can regen- 



* A.I.E.E. Transactions, 69, Part 1, pp. 255 to 268, 1950. 



