A device (250, 260) for coupling a data unit to a digital data signal in a service wiring system that comprises service wiring at least partially contained in wall of a building and a service outlet for connecting to the service wiring, the service wiring concurrently carrying service and digital data signals using frequency division multiplexing; the device comprising: a first service wiring connector (251, 261) having contacts that are directly connectable to the service wiring by engaging complementary contacts in the service outlet (42) without requiring disassembly or alteration of the service outlet (42), a first filter (252, 265) coupled to the first service wiring connector and operative to pass only the digital data signal, and a data connector (258) coupled to said first filter and connectable to a data unit; the service wiring is one out of telephone and CATV wirings and the service outlet is one out of telephone and CATV outlets, and the first service wiring connector (251, 261), the first filter (252, 265) and the data connector (258) are enclosed within a single enclosure having a mechanical attachment (41 a, 41 b) independent of the first service wiring connector (31) for mechanically securing the device to the service outlet (42), and wherein the first wiring service wiring connector is telephone or CATV connectors, and wherein the mechanical attachment is operative to attach the device to a front surface of the service outlet.