Network termination 1

Network Termination 1 (NT1) or Network Termination type 1 refers to equipment in an Integrated Services Digital Network (ISDN) that physically and electrically terminates the network at the customer's premises.[1][2] The NT1 network termination provides signal conversion and timing functions which correspond to layer 1 of the OSI model.[2] In a Basic Rate Interface, the NT1 connects to line termination (LT) equipment in the provider's telephone exchange via the local loop two wire U interface and to customer equipment via the four wire S interface or T interface.[2] The S and T interfaces are electrically equivalent, and the customer equipment port of a NT1 is often labelled as S/T interface. There are many types of NT1 available.

In the United States, the NT1 is considered customer-premises equipment (CPE) and is as such generally provided by the customer or integrated into the customer's equipment. In this case, the U interface is the termination point of the ISDN network. In Europe, the NT1 is generally provided by the provider, and the S/T is the termination point of the ISDN network.[3]