A USB interface having improved EMC immunity where the D+, D\u2212, and USB ground lines each pass through a common mode choke. The detecting device includes a first conductor, a second conductor electrically connected to the second contact, and a warning unit electrically connected between the first contact and the first conductor. Preferably the extension has a lace pattern thereon. The channel can include an opening for venting the dome switch. The device may further comprise a first data transferring connector coupled to the first circuit board at a longitudinal terminus of the hollow slot, wherein the first data transferring connector is adapted to connect to a second data transferring connector that is coupled to the second circuit board.