3.1 Transisters, circuits and batteries
Through the careful addition of traces of certain impurities to semiconductors such as silicon, and the careful juxtaposition of semiconductors treated with different impurities, it is possible to create devices in which the ability to conduct electricity can be controlled by the application of a small voltage. These devices, known as transistors, can operate at very fast rates (switching on and off millions of times per second) in response to an externally applied voltage.
In the latter half of the twentieth century, battery-operated toys equipped with movement, sound and light effects became widely available. The introduction of logic boards allowed further evolutions to occur, from preset control (selecting from a small number of fixed movements, as in Figure 13, left), through corded controllers (allowing real-time control of the toy, as in Figure 13, centre), to using wireless remote controllers (enabling full remote control of all functions, as in Figure 13, right).
The development of low-cost and versatile logic circuits was heralded as a breakthrough in toy design. However, the performance of battery-powered toys was frustratingly still limited by the capacity and weight of their power supplies. This all changed in 1991, when a revolution in battery design occurred, and the first commercial lithium ion battery was manufactured.