OpenR2 is a library that implements the MFC/R2 signalling over E1 lines using

the Zapata Telephony interface (or DAHDI). The MF R2 tones required for the signaling are

generated by code borrowed from the LGPL library SpanDSP written by Steve Underwood,

the user has the option to provide a MF interface to use his own MF R2 tone generation

and detection so the library will use them when needed, that's why this library does not

depend directly on spandsp, libteletone or zaptel for tone generation and detection

(depends on zaptel for ABCD bits and general media transmission though)

You can use this project along with Asterisk to give MFC/R2 support to chan_zap.