MFC – Multi Frequency Compelled. This is a mechanism whereby audio tones are sent down telecommunication circuits in
order to convey signalling information.
R2 – R2 simply refers to Region 2 and R1 is Region 1. Nowadays, protocols have evolved and
been renamed, so the term “R2” is most-commonly used as a nickname for the protocol properly known as
MFC/R2. The term “R1” is not commonly heard at all anymore, certainly not when describing protocols.
MFC/R2 stands for MultiFrequency Compelled/Region 2. Commonly called R2, this protocol is over 60 years old, and used to be a very common signalling mechanism throughout most of the international public telephone
DC signalling has its origins way back in telephony. Battery signalling was extensively employed in early manual systems as a method of interconnecting
switchboards. For CPE to access Switching resources DC Line Signalling was a main staple. Now we have MF4. The last “mile” of the local loop is the last part of a Digital Network that is analogue. End to end ISDN was an earlier attempt to have a full Digital Network.