Discrete semiconductor products are individual, standalone semiconductor devices that are used in electronic circuits and systems. Transistors are a type of discrete semiconductor product that are commonly used to amplify or switch electronic signals. A programmable unijunction transistor, or PUT, is a specific type of transistor that has three layers of alternating p-type and n-type semiconductor material. This allows it to be used as a switch or a voltage-controlled resistor in electronic circuits. PUTs are often used in applications such as timing circuits, pulse generation, and oscillators.