The transistor is a object used in electrical circuits that acts as a valve to control the flow of energy and power of electricity. Developed at Bell Laboratories, the transistor has low power requirements and can be powered by batteries. Transistors amplify sound and are used in microphones, telephones, hearing aids, and radios. Mr. Leland Watson of Maico Hearing Instruments discusses how the hearing aid was the first commercial application of the transistor and how it has led to the miniaturization of the hearing aid.