Abstract: The device comprises a rail (2) inside which two insulating support elements (10) are longitudinally disposed. Said support elements (10) are provided with projecting portions (10a) housing respective wires (11) provided with mutually facing contact surfaces (11a). The latter slightly project with respect to the projecting portions (10a) so that they can come into contact with contact elements (16) extending from a connection shank (13) and substantially flush therewith. The connection shank (13) is part of an adaptor (3) to which a safety low-tension-operated utilization unit can be connected and is engageable with rail (2) through a longitudinal opening (4a).