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 wherein the system interacts, when an external energising force is imposed on the system, causing the members to respond due to their kinematic and dynamic characteristics, thereby creating relative motion between the members; at least one trigger member coupled 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, wherein, 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; characterised in that 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 at least one trigger member rate of movement with respect to the first member and this rate of movement is in turn governed by a magnetic flux interaction 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, the eddy current force resisting movement of the trigger member with respect to the first member. 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 wherein the system interacts, when an external energising force is imposed on the system, causing the members to respond due to their kinematic and dynamic characteristics, thereby creating relative motion between the members; at least one trigger member coupled 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, wherein, 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; characterised in that 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 at least one trigger member rate of movement with respect to the first member and this rate of movement is in turn governed by a magnetic flux interaction 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, the eddy current force resisting movement of the trigger member with respect to the first member.