Adapter (1) for the modular connection of electrical devices (2) to a bar-based electricity distribution system (4), featuring a clamping device (31) for the electrical connection to the oars (4) and a conductor (33), forming an integral part of the clamping device (31), for the electrical connection of the device (2), such that the clamping device (31) is located on the side (3) of the adapter (1) facing the bars (4) with the connection axis (47) aligned with the axis (48) of one bar (4), which features a slider (34) on the side of the adapter (1) opposite the clamping device (31), the said slider (34) supporting the device (1) being geometrically coupled to the body (30) of the adapter (1) and being able to slide in relation to the adapter (1) to permit the insertion and withdrawal of the end (37) of the contact of the conductor (33) in the device (2) and with the opposite edges (8, 9) of the adapter (1) featuring flanges (10, 11) for connection to a supporting structure (7).