The UK0 interface is used to transmit the two B channels at 64 kbit/s each, the D channel at 16 kbit/s, and synchronization and maintenance information. This results in a gross bit rate of 160 kbit/s. Since only the normal copper twisted pair between the local exchange and the network termination unit( NTBA) is available for an ISDN subscriber, the ISDN bit stream must be transmitted full- duplex via the existing telephone cables.
The UK0 interface uses the same transmission technique as the basic access, echo cancellation. The range of this two- wire interface is between 7 and 9 km, depending on the line diameter. This interface can be used to extend the S0 shunt connection. The UK0 interface uses different line codes on the network side: the quaternary 4B3T coding( MMS43) is used in Germany and a 2B1Q coding is used in Europe.