a front bracket, said front bracket comprising an elongated face panel, a plurality of openings cut through the face panel of said front bracket and arranged in line along the length of the face panel of said front bracket, a plurality of mounting through holes symmetrically disposed at two distal ends of the face panel of said front bracket for mounting, a first side panel perpendicularly extended along one side of the face panel of said front bracket, a plurality of mounting lugs respectively perpendicularly extended from one side of said first side panel remote from the face panel of said front bracket, said mounting lugs each having a locating hole, a second side panel perpendicularly extended along an opposite side of the face panel of said front bracket, and a springy flange extended from a middle part of one side of said second side panel remote from the face panel of said front bracket;

a rear bracket, said rear bracket comprising an elongated face panel, a plurality of openings cut through the face panel of said rear bracket corresponding to the openings of said front bracket, a plurality of locating holes respectively fastened to the locating holes of the mounting lugs of said front bracket by a respective fastening member, a side panel perpendicularly extended along one long side of the face panel of said rear bracket and attached to an outer side of the springy flange of said front bracket, two springy flanges respectively extended from one side of the side panel of said rear bracket remote from the face panel of said rear bracket and attached to an inner surface of the second side panel of said front bracket, and two end panels respectively perpendicularly extended from two ends of the face panel of said rear bracket; and

a plurality of jack modules respectively mounted in the openings of said front bracket and the openings of said rear bracket, said jack modules each comprising:

a front housing, said front housing comprising two parallel rows of mounting slots, a set of terminal grooves formed in each of the mounting slots of said front housing, an upper circuit board mounting space and a lower circuit board mounting space defined at a rear side thereof at different elevations in communication with the two parallel rows of mounting slots of said front housing respectively, two upper insertion holes disposed in communication with two distal ends of the upper circuit board mounting space of said front housing, two lower insertion holes disposed in communication with two distal ends of the lower circuit board mounting space of said front housing, a plurality of hooks and hook holes symmetrically formed on top and bottom walls thereof, a plurality of mounting lug extended from two distal ends thereof for fastening to said front bracket, and a plurality of top and bottom retaining blocks respectively secured to said front bracket;

a rear housing, said rear housing comprising two parallel rows of mounting slots, a set of terminal grooves formed in each of the mounting slots of said rear housing, an upper circuit board mounting space and a lower circuit board mounting space defined at a rear side thereof at different elevations in communication with the two parallel rows of mounting slots of said rear housing respectively, two upper insertion holes disposed in communication with two distal ends of the upper circuit board mounting space of said rear housing, two lower insertion holes disposed in communication with two distal ends of the lower circuit board mounting space of said rear housing, a plurality of hooks and hook holes symmetrically formed on top and bottom walls thereof and respectively fastened to the hook holes and hooks of said front housing, and a plurality of top and bottom retaining blocks respectively secured to said rear bracket; and

a first circuit board and a second circuit board, said first circuit board and said second circuit board each comprising two rows of terminal blocks, multiple sets of conducting terminals respectively installed in said terminal blocks in two reversed directions, said first circuit board having a front half inserted into the upper circuit board mounting space of said front housing to force the terminals of the respective terminal blocks into the respective terminal grooves of the respective mounting slots of said front housing and a rear half inserted into the upper circuit board mounting space of said rear housing to force the terminals of the respective terminal blocks into the respective terminal grooves of the respective mounting slots of said rear housing, said second circuit board having a front half inserted into the lower circuit board mounting space of said front housing to force the terminals of the respective terminal blocks into the respective terminal grooves of the respective mounting slots of said front housing and a rear half inserted into the lower circuit board mounting space of said rear housing to force the terminals of the respective terminal blocks into the respective terminal grooves of the respective mounting slots of said rear housing.