Abstract: A jack-type plug in the form of a connecting plug includes a central contact pin for one conductor and a resilient contact element in the region of the outside surface of the plug for the other conductor, the plug having an axially elongate male part for mating with a female part constituting a part of the current socket receiving the plug. To enable the same plug to be used for two differently dimensioned current sockets the male part in forming of two parts with different cross-sectional dimensions so that the one male part mates with the female part of a current socket and the other male part mates with the female part of another socket, this part having a different cross-sectional area from the first mentioned female part. In addition, the smaller male part carries the central contact pin and is movable in the larger male part, but no farther than to permit the pin to remain axially projecting outside the larger male part.