Network Terminator One

Device for Basic Rate ISDN (BRI) that converts the two off-premises signal wires to four-wire connections suitable for an ISDN telephone. An NT1 is often designed to support multiple four-wire connections, for example, one for a telephone and one for a fax machine. The NT1 is physically connected between the ISDN board of a videoconferencing system and the ISDN phone line. The NT1 supports network maintenance functions such as loop testing.