Duplex socket with a socket-based residual current device, comprising connection parts for the electrical plugs of two electrical devices, which socket is provided with an inbuilt residual current device (1) based on magnetic tripping and with a summation current transformer (23) which residual current device (1) comprises a main switch with knob (301), a trip coil (303) and also a permanent magnet (306), wherein the knob (301) of the main switch is arranged beside the socket parts at essentially the same distance from both socket parts, which socket can be installed as a flush-mounted or furnishing-mounted installation, in which there are two recessed socket parts (15a, 15b, 103) of the shape of the counterpart of an electrical plug that are fitted below the top surface of the face plate (13, 102), and the electrical connection parts for two electrical plugs of an electrical device fitted into them, which residual current device is an integrated main switch-trip part (1, 100) provided with a metallic shaft (308) traveling through a trip coil (303) and with a permanent magnet (306) arranged below it, in which case the main switch is simultaneously a contact that opens in a residual current protection situation, and wherein the center axis (308) of the main switch-trip part is arranged with the center axes of the socket parts (15a, 15b, 103) into an isosceles triangle such that the center axes of the socket parts are the feet of the triangle and the center axis (308) of the main switch-trip part is its pinnacle.