These solutions are extensions of IP PBX and unified messaging (UM) products. In many cases, UM is tightly integrated with PBX; in others, the two are offered by separate vendors. The functionality offered is telephony-centric and typically includes: one-number service, supporting phone twinning, softphones (which may be proprietary), remote phones (phone login over the Internet) and fixed-mobile convergence (FMC). Examples of PBX- and IP PBX-centric solutions include all the leading PBX vendors.