Is the tendency for different technological systems to evolve towards performing similar tasks. Convergence can refer to previously separate technologies such as voice (and telephony features), data (and productivity applications) and video that now share resources and interact with each other, synergistically creating new efficiencies. A clear trend is emerging in the form of fixed and mobile telephony convergence (FMC). The aim is to provide both services with a single phone, which could switch between networks ad hoc. Several industry standardisation activities have been completed in this area such as the Voice call continuity (VCC) specifications defined by the 3GPP.