2-wire line-side local switching system port that uses the 2B1Q line code at a 160 kilobit per second rate to transport overhead and up to two B channels and one D channel.

The version of ISDN which consist of two 64 kbit/sec channels for speech or data, plus a 16 kbit/sec channel used for signalling and control.

The Basic Rate ISDN interface provides a bandwidth of 144Kbit/s which is divided into two bearer channels of 64Kbit/s each and one data (D) channel for signalling with an available bandwidth of 16Kbit/s.