Abstract: A coaxial jack with an internal switch mechanism and a shielded signal conductor includes a cylindrical shell having an axial opening, and an elongate signal conductor supported coaxially inside the shell, and surrounded by a shield that includes an access window positioned so that a portion of the signal conductor is accessible. A back end of an elongate resilient switch contact is fixed by a switch contact support at a back portion of the shell on one side of the shell axis. The switch contact extends inside the shell toward the front opening at a certain inclination and has a free end located on a side of the shell axis opposite the one side. The switch contact is configured and positioned to make an electrical connection with the signal conductor, via the access window in the shield, in the absence of a mating plug. An elongate actuator is supported on the inner periphery of the shell and has an engaging part that protrudes into a defined plug travel path inside the shell.