The present document specifies the physical and electrical characteristics (except safety, overvoltage and EMC aspects) and corresponding test principles for a terminal equipment interface for connection to the network termination points of Open Network Provision (ONP) ordinary quality or special quality voice bandwidth 4-wire analogue leased lines defined by EN 300 451 and EN 300 452. The present document is written only to ensure that the interface of the terminal equipment is compatible with the ONP ordinary quality or special quality voice bandwidth 4-wire analogue leased line. It is applicable to all interfaces designed for connection to these leased lines, 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.