Asterisk Discovers Again Why Open Source is a Star

Call me parochial, but until a few minutes ago, I'd never heard of MFC/R2, and certainly had no inkling it might be important. Apparently:

MFC/R2 is a telephony signaling protocol, which dates back over 50 years. Its full name is the Multifrequency Compelled R2 Signaling System. It was originally used to provide register to register (i.e. switch to switch) signaling over analogue copper pair wiring at a higher speed than had been possible with pulse dialing....

On Open Enterprise blog.