The R2 MFC is basically one of the standard signaling which can be used to establish a call between to different equipments such as, telephone switch with other one and PBX’s with local exchange. Using E1 or T1 connection. There is two main signaling, line signaling and register signaling. Line signaling is the one which send (seizer, seizer ack., release, clear back.etc.) signaling and Register signaling is the part that send the (A-number, B-number and the calling category).
Because of long call setup time and less call information in the R2 MFC, the most of connection today is using SS7 signaling which have more speed and features than R2 MFC signaling.