The present document specifies the physical and electrical characteristics (except safety@ over voltage and EMC aspects)@ the necessary functional characteristics and the corresponding test principles for a terminal equipment interface for connection to the Network Termination Points (NTPs) of Open Network Provision (ONP) 2 048 kbit/s digital structured leased lines using 120 ?? interfaces with an information transfer rate of 1 984 kbit/s without restriction on binary content. The present document is to ensure that the interface of the terminal equipment is compatible with the ONP 2 048 kbit/s digital structured leased line. A terminal equipment interface that conforms to the present document will also be compatible with an ONP 2 048 kbit/s unstructured leased line. The present document is applicable to all interfaces designed for connection to the leased line@ however in the cases of apparatus that carries a particular service@ of complex apparatus and of apparatus in private networks@ other requirements may apply in addition to the present document. Customer premises wiring and installation between the terminal equipment and the NTP are outside the scope of the present document.