Automatic Message Accounting - Centralized AMA

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 on connecting the call, an answer entry when the called party 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 × 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.