Use the Multifrequency (MF) signaling feature to perform signaling used between media servers and the Central Office (CO). It is similar to dual-tone multifrequency (DTMF) signaling in that tones convey the dialed number.

With MF signaling, the signal is usually a combination of two frequencies from a group of 5 or 6 frequencies (2/5 or 2/6). The origination and destination servers or switches exchange tones that have specific meanings according to the MF protocol.