The key assembly comprises a keycap having a touchsurface for receiving a press force that moves the keycap from an unpressed position toward a pressed position. In preferred embodiments, the training units are individual systems comprising training software running on a turn-key based personal computer. Modulating the current limit reference could include modulating a reference current based on a product of first and second input currents. The needle has an angled bend which directs the tip of the needle substantially perpendicular to the skin-contacting surface. What is thus made possible is that, disregarding the frequency of the clock signal to be delayed and the length of the delay time, the complementary delayed clock signals always have the same phase angle with respect to one another. Global entities are entities that are referenced by one or more non-local entities.