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Automatic Number Identification:

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  1. C. H. Dagnall, Jr. Automatic Number Identification: Outpulsers and Identifiers The Bell System is continuously devising ways to bring all of its switching systems into the scheme of the entirely automatic completion of calls. One of the latest of these ways is the Auto- matic Number Identification System (RECORD, June, 1960). ANI was developed to identify the directory number of a calling customer and trans- mit this number to a tandem or toll point having Centralized Automatic (CAMA) equipment. A common -control type of system, it uses relays and electronic circuitry. number. Automatic identification not only saves time for the customer, but also avoids the pos- sibility of human error. Panel, No. 1 crossbar, or step -by -step switching equipment is used in all of the local dial offices in- stalled by the Bell System before 1948. The ANI system, plus direct -distance dialing switching fea- tures, added to these offices enable them to offer the same DDD service as newer No. 5 crossbar offices, permitting customer dialing all over the country with a minimum of equipment needed for charging purposes. This article will deal specifically with two of the components in ANI- outpulsers and identi- fiers. To understand their features requires first a brief look at the operation of ANI. Perhaps the most logical way to look is to examine the circuits in the order in which they come into action. The first of these are the "trunk" circuits. A trunk circuit (in this case, not the custom- ary pair of wires) is inserted between the switch- es of the existing central office and a pair of wires to the tandem or toll CAMA office. One function of the trunk circuit is to determine when a called number has been transmitted to the CAMA office. Message Accounting ANI will serve three types of central offices - panel, No. 1 crossbar, and step -by -step. For these three switching methods, the system will permit fully Automatic Message Accounting (AMA) for extended -area and direct- distance dialed calls without an operator. When a telephone customer originates a toll call, ANI identifies his directory number and sends it to a tandem or toll office where CAMA equipment records the information needed to charge for the call. This fully automatic treat- ment takes the place of operator identification of customer dialed calls -a system in which an oper- ator enters the connection to ask for the calling 97 March 1961