A catheter, comprising an elongated catheter body (12) and a control handle (16) proximal of the elongated catheter body, the control handle having:a barrel (80) housing a piston (54) in a telescopic configuration, the piston having a thumb control (56), the piston configured for longitudinal movement relative to the housing by a user via the thumb control for deflecting the tubing； and a tension adjustment assembly including:a force member adapted for applying a force on the piston and a knob rotationally coupled to the force member, the knob adapted for rotation by the user to adjust the force applied on the piston by the force member.
