Which of the following is NOT one of the major oscillator circuits found in radio equipment?

The correct answer highlights that the Tank circuit, while important in radio frequency applications, is not classified as a major oscillator circuit. Oscillator circuits are specifically designed to generate continuous wave signals, and they typically employ specific configurations to create oscillation.

The Colpitts, Hartley, and Pierce circuits are all well-known types of oscillators. The Colpitts oscillator utilizes a combination of capacitors and inductors to produce oscillations, making it suitable for a variety of RF applications. The Hartley oscillator is similar but uses a tapped inductor as part of its feedback network, also allowing it to generate oscillations effectively. The Pierce oscillator, on the other hand, is predominantly used for generating high-frequency signals and is based on a crystal as part of its feedback loop to ensure stability and precision in frequency generation.

In contrast, the Tank circuit generally refers to an LC circuit (inductor-capacitor) that is used to select specific frequencies or to filter signals rather than generate them. While it is an essential concept in radio technology, it does not function as an oscillator itself. Understanding the roles of these circuits is crucial for grasping how radio equipment works and how signals are processed.