The NT-1 (Network Termination 1) is a device that is required to connect ISDN terminal equipment to an ISDN line. The NT1 is a device which provides the interface between the two-wire twisted pairs used by telephone companies in their ISDN Basic Rate (BRI) network and an end-user's four-wire terminal equipment.
Meaning of NT-1 in English
DAX English glossary of key connectivity terms. Английский глоссарий основных терминов по коммуникациям DAX. 2012