An electrical connector (2, 3) provides an interface compatible with an internal micro Serial ATA connector. The electrical connector (2, 3) includes an insulated housing (21, 31), a first number of contacts (221, 222, 223, 321, 322, 323) assembled to the insulated housing (21, 31); and a second number of contacts (224, 225, 324, 325) assembled to the insulated housing (21, 31). The first number of contacts (221, 222, 223, 321, 322, 323) constitute a power segment and a signal segment compatible with the internal micro Serial ATA connector. The second number of contacts (224, 225, 324, 325) is used for mating with a new type of mating connector (3, 2) when higher transfer speed is needed.