A Network Interface Unit (NIU) for serving a central office line and one or more local stations by interfacing remotely monitored devices, such as utility controllers and meter readers, to an existing customer telephone line that serves the customer site. The NIU comprises a master switching unit having a central office port, a main port connected to one or more telephone sets on the customer premises, and at least one station port assigned a calling identity and connected to a remotely monitored or controlled device. The NIU also comprises a controller for establishing "standby" and "armed" states in response to any one of a plurality of predefined sequences of normal power ringing signals. After receipt of a predefined sequence of normal power ringing signals, the NIU is "armed" such that it is capable of receiving a Telemetry and Remote Control call from Telemetry And Control (TAC) hub equipment and, if the call is received within a predefined period of time, enabling two-way communication between the TAC hub equipment and the remote device.