An electrical connector comprising a housing having a mating face and a mounting face, and a plurality of differential pairs of terminals extending between the mating face and the mounting face, each of the differential pairs comprising a positive terminal and a negative terminal having positive and negative mating contacts, respectively, arranged in a pattern at the mating face, and positive and negative mounting contacts, respectively arranged in a pattern, at the mounting face, characterized in that: the differential pairs are arranged in a first group (86b, 90b) and a second group (86a, 90a), wherein for each of the differential pairs of the first group (86b, 90b), the positive (20 7, 20 9, 20 11) and negative (20 8, 20 10, 20 12) mating contacts are arranged in the pattern at the mating face in a first orientation, and the positive (42 7, 42 9, 42 11) and negative (42 8, 42 10, 42 12) mounting contacts are arranged in the pattern at the mounting face in a second orientation, and if the patterns (84, 82) at the mating face and the mounting face are overlaid, the positive and negative mounting contacts of the first group (86b, 90b), are arranged in the pattern at the mounting face in the second orientation which is inverted by 180° relative to the first orientation, and wherein for each of the differential pairs of the second group (86a, 90a) the positive (20 1, 20 3, 20 5) and negative (20 2, 20 4, 20 6) mating contacts are arranged in the pattern at the mating face in a first orientation, and the positive (42 1, 42 3, 42 5) and negative (42 2, 42 4, 42 6) mounting contacts are arranged in the pattern at the mounting face in a second orientation and if the patterns (84, 82) at the mating face and the mounting face are overlaid, the positive and negative mounting contacts of the second group (86a, 90a) are arranged in the pattern at the mounting face in the second orientation which is common to the first orientation. the differential pairs are arranged in a first group (86b, 90b) and a second group (86a, 90a), wherein for each of the differential pairs of the first group (86b, 90b), the positive (20 7, 20 9, 20 11) and negative (20 8, 20 10, 20 12) mating contacts are arranged in the pattern at the mating face in a first orientation, and the positive (42 7, 42 9, 42 11) and negative (42 8, 42 10, 42 12) mounting contacts are arranged in the pattern at the mounting face in a second orientation, and if the patterns (84, 82) at the mating face and the mounting face are overlaid, the positive and negative mounting contacts of the first group (86b, 90b), are arranged in the pattern at the mounting face in the second orientation which is inverted by 180° relative to the first orientation, and wherein for each of the differential pairs of the second group (86a, 90a) the positive (20 1, 20 3, 20 5) and negative (20 2, 20 4, 20 6) mating contacts are arranged in the pattern at the mating face in a first orientation, and the positive (42 1, 42 3, 42 5) and negative (42 2, 42 4, 42 6) mounting contacts are arranged in the pattern at the mounting face in a second orientation and if the patterns (84, 82) at the mating face and the mounting face are overlaid, the positive and negative mounting contacts of the second group (86a, 90a) are arranged in the pattern at the mounting face in the second orientation which is common to the first orientation.