The UK2 interface is an ISDN interface for the network termination at the primary multiplex connection in ISDN
. The UK2 interface is a four-wire interface with twisted copper wires. The interface is defined in the ITU-T recommendations G.703, G.704 and G.705. Remote basic access multiplexers can also be connected to the digitalexchange technology for the local service (DIVO) via this interface. If an optical fibre is used as the transmission medium, the interface is called UG2.