The most accurate escapements, such as the deadbeat, approximately satisfy this condition. At first, Meyer and employees concentrated on manufacturing cylinder escapements. These watches had pin-pallet escapements rather than platform escapements. Gravity escapements were used in tower clocks. Most tourbillons use standard Swiss lever escapements, but some have a detent escapement. A detent escapement has a strong advantage over other escapements as it needs no lubrication. Grasshopper escapements made by Harrison in the 18th century are still operating. The keys of the keyboard are connected by vertical pushrods to the escapements. Even with single channel radios, a sequence of escapements could sometimes be cascaded. Most escapements wear far more quickly, and waste far more energy. Both Robin and Fasoldt escapements give impulse in one direction only. In the late 19th century, electromechanical escapements were developed for pendulum clocks. Verge escapements were used in virtually all clocks and watches for 400 years. Escapements are also used in other mechanisms besides timepieces. Escapements play a big part in accuracy as well.