The plug socket has an insulating socket housing (1) with a central pair of socket sleeves (2) combined with an auxiliary function module which is mechanically and electrically coupled to the plug socket. The socket housing is positioned asymmetrically relative to the socket sleeves to leave a free space (5) above it for housing at least part of the auxiliary function module. The free space may occupy between 1/2 and 1/3 of the socket surface area.
