A connector for signal transmission includes an inner cap, a conductive part and an outer cap. The inner cap is made of hard insulation material with a cylindrical shape, providing a central inner hole, having a small sized fitting post at a front end thereof corresponding a neck hole of an input/output hole in a distributor of a cable television line and having a reduced outer diameter at a rear end thereof so as to form a joint between the front end thereof and the rear end thereof. The conductive part is made of conductive metal, having a shape of pin at an end thereof and having a trumpet opening formed by at least two metal strips at another end thereof. The outer cap is made of hard insulation material with a cylindrical shape too, having a front end thereof being an open end and a rear end thereof being a close end, a central outer hole being provided at the rear end, a fitting chamber being formed therein for communicating with the outer hole and the front end having a wall thickness corresponding to the input/output hole at an inner diameter thereof and the inner cap at an outer diameter thereof, respectively. The conductive part can be inserted into the inner hole with the pin part thereof extending outward the fitting post and an axial exertion can force the outer cap to be sandwiched between the inner wall of the input/output outer cap and the outer wall of the inner cap tightly.