Automatic Message Accounting
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Automatic Messaging Accounting (AMA) provides detail billing for telephone calls. When Direct Distance Dialing (DDD) was introduced, 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.
[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.
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" in Message Rate service lines, in Panel switches and similar exchanges installed in the first half of the 20th Century. The 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. American registers generally showed four digits.
Despite the arrival of STD, Europe continued making and using message registers in the 1960s, designing ones that could register more than one click per second on a long distance call and display five or six digits.
