1947 First pointcontact transistor John Bardeen, Walter H. Brattain, and William B. Shockley of Bell Labs discover the transistor. Brattain and Bardeen build the first pointcontact transistor, made of two gold foil contacts sitting on a germanium crystal. When electric current is applied to one contact, the germanium boosts the strength of the current flowing through the other contact. Shockley improves on the idea by building the junction transistor�"sandwiches" of N- and P-type germanium. A weak voltage applied to the middle layer modifies a current traveling across the entire "sandwich." In November 1956 the three men are awarded the Nobel Prize in physics. 1952 First commercial device to apply Shockley�s junction transistor Sonotone markets a $229.50 hearing aid that uses two vacuum tubes and one transistor�the first commercial device to apply Shockley�s junction transistor. Replacement batteries for transistorized hearing aids cost only $10, not the nearly $100 of batteries for earlier vacuum tube models. 1954 First truly consistent mass-produced transistor is demonstrated Gordon Teal, a physical chemist formerly with Bell Labs, shows colleagues at Texas Instruments that transistors can be made from pure silicon�demonstrating the first truly consistent mass-produced transistor. By the late 1950s silicon begins to replace germanium as the semiconductor material out of which almost all modern transistors are made. 1954 First transistor radio Texas Instruments introduces the first transistor radio, the Regency TR1, with radios by Regency Electronics and transistors by Texas Instruments. The transistor replaces De Forest�s triode, which was the electrical component that amplified audio signals�making AM (amplitude modulation) radio possible. The door is now open to the transistorization of other mass production devices.