Automatic Message Accounting
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Automatic Message Accounting (AMA) provides detail billing for telephone calls. When Direct Distance Dialing (DDD) was introduced in the USA, message registers no longer sufficed for dialed telephone calls. The need to record the time and phone number of each long distance call was met by electromechanical data processing equipment.
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[edit] Centralized AMA
In Centralized AMA (CAMA) the originating Class 5 telephone switches used Automatic number identification (ANI) and Multi-frequency (MF) to send the originating and dialed phone numbers to the Class 4 Toll Connecting office. The Class 4 office had punched tape machines to record this information on a long strip of paper the width of a hand. Each day a technician cut the paper tapes and sent them to the Accounting Center to be read and processed into phone bills. Each punch recorder was responsible for 100 trunks, and its associated Call Identity Indexer (CII) identified the trunk for an Initial Entry upon connecting the call, an Answer Entry when the called end answered, and a Disconnect Entry when the call was cleared.
In Bell System exchanges (particularly 5XB switches) information from the Marker told the Sender that the call required ANI, and stored the calling equipment number in reed relay packs in the sender. The sender used the Transverter Connector (TVC) to seize a Transverter (TV), which was a bay of a few hundred flat spring relays that controlled all AMA functions. TV looked in the AMA Translator (AMAT) that took care of these particular few thousand lines. AMAT was a rack of ferrite ring cores with cross-connect wires passing through holes of 3 x 4 inches or about a decimeter square, one wire per line. The wire was terminated on a wire wrap peg representing that particular line, and passed through a ring that represented the NNX digits of the billing number, then the M, C, D and finally Units of that number. When queried, AMAT sent a high current pulse through the wire for that particular line, inducing pulses in the appropriate rings which were amplified by a cold cathode tube amplifier and then by a relay, and sent back to the Transverter which supplied it to the Sender for transmission by ANI to the Tandem office.
In case of billing complaint, a test apparatus allowed scanning through all the lines in an office at the rate of about a hundred per minute, to find which ones were translated to a particular billing number.
[edit] Local AMA
In Local AMA (LAMA) all this equipment was located at the Class 5 office. In this case, it also recorded the completion of local calls, thus obviating message registers. For detail billed calls, the punch recorded both calling and called numbers, as well as time of day. For message rate calls, only the calling number and time of day.
In some electromechanical offices in the 1970s, the paper tape punch recorders were replaced by magnetic tape recorders. Most punches remained in service until the exchange switch itself was replaced by more advanced systems. Stored Program Control exchanges, having computers anyway, do not need separate AMA equipment. They sent magnetic tapes to the Accounting Center until approximately 1990, when data links took over this job.
[edit] Message Register
Electromechanical pulse counters counted "Message Units" for Message Rate service lines, in Panel switches and similar exchanges installed in the early and middle 20th Century. The metering pulses were generated in a junctor circuit, at a rate set by the sender, usually one pulse every few minutes. Every month a worker wrote down the indicated number of message units, similar to a gas meter. In the middle 20th century it became customary to photograph the meters, about a hundred per film frame, for examination in comfort. Since they were only used on local calls, and most residential lines didn't pay for local calls, American message registers generally showed four digits.
Despite the arrival of STD, Europe continued making and using message registers in the 1970s, designing ones that could register more than one click per second on a trunk call and display five or six digits.
