The 3G CDMA standards, the Femtocell Convergence Server (FCS) is a network element which interworks between all femtocells and the CDMA core voice network. It looks to the rest of the core network like an MSC (Mobile Switching Center), or voice switch - sending and receiving the same messages to setup and teardown voice calls with other subscribers. It handles many thousands (or tens of thousands) of femtocells through direct IP connections, which are securely encrypted with IPsec and decoded by a specialist IPsec security gateway.