A housing for a filtering device with a terminal block for connecting into an electrical grid, wherein the said terminal block comprises: - a socket outlet box with at least two horizontal seats with partitions and a vertical dividing wall with openings at one end of the seats, the openings being adapted to receive connecting wires of a filtering device or any other electronic device, - at least two connection terminals, which are mounted in the horizontal seats of the socket outlet box, each of the connection terminals being provided with a longitudinal borehole and with at least two perpendicular threaded holes (32, 33), one each end of each connection terminal, the threaded hole on the filtering device end is provided with a screw for fastening a connecting wire from the filtering device, while the threaded hole on the other end of the connection terminal is provided with a screw for fastening an electrical grid conductor, - an upper portion of the terminal block is attached to the socket outlet box and formed so as to cover the horizontal seats and the connection terminals, so that the screws for fixing the electrical grid conductors are accessible from the outside of the terminal block via openings and the upper portion is shaped such that together with the socket outlet box it forms openings for the electrical grid conductors to be inserted, wherein the openings are accessible from the outside of the terminal block, characterized in that a cover is provided on the upper part of the terminal block through which the screws of the connection terminals are accessible via openings, wherein said cover is configured to cover the openings and the screws in the threaded holes in order to prevent contact and unscrewing of the screws when voltage is applied. - a socket outlet box with at least two horizontal seats with partitions and a vertical dividing wall with openings at one end of the seats, the openings being adapted to receive connecting wires of a filtering device or any other electronic device, - at least two connection terminals, which are mounted in the horizontal seats of the socket outlet box, each of the connection terminals being provided with a longitudinal borehole and with at least two perpendicular threaded holes (32, 33), one each end of each connection terminal, the threaded hole on the filtering device end is provided with a screw for fastening a connecting wire from the filtering device, while the threaded hole on the other end of the connection terminal is provided with a screw for fastening an electrical grid conductor, - an upper portion of the terminal block is attached to the socket outlet box and formed so as to cover the horizontal seats and the connection terminals, so that the screws for fixing the electrical grid conductors are accessible from the outside of the terminal block via openings and the upper portion is shaped such that together with the socket outlet box it forms openings for the electrical grid conductors to be inserted, wherein the openings are accessible from the outside of the terminal block, characterized in that a cover is provided on the upper part of the terminal block through which the screws of the connection terminals are accessible via openings, wherein said cover is configured to cover the openings and the screws in the threaded holes in order to prevent contact and unscrewing of the screws when voltage is applied.