Abstract: A simple and compact light interrupting inertial sensor for brake controls in which a dampening restraint is magnetic. A pendulum structure on a rigid arm is pivotal in a unidirectional or omnidirectional sense and the pendulum weight mass is magnetically attracted and is secured by magnetic attraction against premature movement. The magnet element provides an adjustable attraction by variation in proximity to the magnetically attracted member to provide a high initial resistance to movement and a fast decay of holding force at the threshold of force required for breakaway.