A device comprising: at least one first member in a kinematic relationship with at least one further member to form a system, the system moving within a limited range of motion and wherein the system interacts when an external energizing force is imposed on the system causing the members to respond due to their kinematic and dynamic characteristics and thereby creating relative motion between the members; at least one trigger member coupled to, and adjacent to the at least one first member said at least one trigger member moving with respect to the first member in response to a pre-determined system movement and, when the at least one trigger member moves, the at least one trigger member or a part thereof imposes a braking action on the system or a member or members thereof, by an interaction between the trigger member and the further member , resisting relative movement between the trigger member and the further member ; and, wherein the speed and/or intensity of the braking action imposed by the at least one trigger member on the system or a member or members thereof is controlled by the rate of movement of the at least one trigger member relative to the first member and this rate of movement is in turn governed by a magnetic flux interaction that is at least partially orthogonal to the direction of relative motion between the at least one trigger member or a part thereof and the at least one first member or a part thereof causing formation of a magnetically induced eddy current force between the at least one trigger member or a part thereof and the at least one first member or a part thereof, wherein the magnetic flux interaction provides tunable resistance, changing the rate of movement between the members, and the magnitude of the tunable resistance is varied in a consistent manner as the members move or in a stepped or otherwise varied manner. at least one first member in a kinematic relationship with at least one further member to form a system, the system moving within a limited range of motion and wherein the system interacts when an external energizing force is imposed on the system causing the members to respond due to their kinematic and dynamic characteristics and thereby creating relative motion between the members; at least one trigger member coupled to, and adjacent to the at least one first member said at least one trigger member moving with respect to the first member in response to a pre-determined system movement and, when the at least one trigger member moves, the at least one trigger member or a part thereof imposes a braking action on the system or a member or members thereof, by an interaction between the trigger member and the further member , resisting relative movement between the trigger member and the further member ; and, wherein the speed and/or intensity of the braking action imposed by the at least one trigger member on the system or a member or members thereof is controlled by the rate of movement of the at least one trigger member relative to the first member and this rate of movement is in turn governed by a magnetic flux interaction that is at least partially orthogonal to the direction of relative motion between the at least one trigger member or a part thereof and the at least one first member or a part thereof causing formation of a magnetically induced eddy current force between the at least one trigger member or a part thereof and the at least one first member or a part thereof, wherein the magnetic flux interaction provides tunable resistance, changing the rate of movement between the members, and the magnitude of the tunable resistance is varied in a consistent manner as the members move or in a stepped or otherwise varied manner. <EOS>