In centralized AMA (CAMA), the originating Class 5 telephone switches used automatic number identification (ANI) and multi-frequency (MF) signaling to send the originating and dialed telephone numbers to the Class 4 toll connecting office.
In Bell System telephone exchanges, particularly the 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.