Escapement The independent watchmaker, De Bethune, has developed a concept where a magnet makes a resonator vibrate at high frequency, replacing the traditional balance spring. In the late 19th century, electromechanical escapements were developed for pendulum clocks. In these, a switch or phototube energised an electromagnet for a brief section of the pendulum's swing. On some clocks the pulse of electricity that drove the pendulum also drove a plunger to move the gear train. In 1843 Matthäus Hipp first mentioned a purely mechanical clock being driven by a switch called "echappement à palette". A varied version of that escapement has been
Mechanical energy isolated system remains constant in time, as long as the system is free of friction and other non-conservative forces. In any real situation, frictional forces and other non-conservative forces are present, but in many cases their effects on the system are so small that the principle of conservation of mechanical energy can be used as a fair approximation. Though energy cannot be created or destroyed in an isolated system, it can be converted to another form of energy. In a mechanical system like a swinging pendulum subjected to the conservative gravitational force where frictional forces like air drag and friction