This Recommendation describes the interface between the telecommunications network and the customer installation in terms of their interaction and electrical characteristics. This Recommendation allows the transmission of POTS and V-series data services simultaneously with a digital channel over a single mixed gauge twisted metallic pair. Annex C defines the procedures to operate in a TCM-ISDN noise environment. Operation in the frequency band over BRA-ISDN is for further study. This Recommendation includes procedures to allow provisioning without the need for splitters, typically installed at the ingress to the customer premises. Additionally, power management procedures and link states are specified to achieve power savings at the central office and customer premises.