Sinusoidal Oscillator
A sinusoidal oscillator is an electronic circuit that is capable of producing a sinusoidal waveform, which is a continuous and periodic waveform. It is an essential component in many electronic devices and systems, as it provides a stable and reliable source of oscillation.

There are several types of sinusoidal oscillators, each with its own characteristics and applications. In this question, we are asked to identify the example that is not a sinusoidal oscillator among the given options.

RC Phase Shift Oscillator
The RC phase shift oscillator is a type of sinusoidal oscillator that uses an RC network to provide the necessary phase shift for oscillation. It consists of an amplifier and a feedback network composed of resistors and capacitors. The phase shift introduced by the network allows the amplifier to provide positive feedback, resulting in sustained oscillations. This oscillator is commonly used in audio and communication systems.

Weinbridge Oscillator
The Weinbridge oscillator is another type of sinusoidal oscillator that employs a bridge network and an operational amplifier to generate the oscillations. It uses a combination of resistors, capacitors, and an inductor in a bridge configuration to achieve the desired phase shift. The feedback network is connected to the operational amplifier, which amplifies and feeds the output back to the input. This oscillator is widely used in audio applications, such as audio tone generation and music synthesis.

Crystal Oscillator
The crystal oscillator is a highly stable and accurate type of sinusoidal oscillator that utilizes the properties of a piezoelectric crystal to generate the oscillations. The crystal acts as a resonator, vibrating at a specific frequency when an electric field is applied. The crystal is connected to an amplifier circuit, which amplifies the oscillations and provides the necessary feedback for sustained oscillations. This oscillator is commonly used in electronic devices that require precise timing, such as clocks, computers, and communication systems.

Blocking Oscillator
The blocking oscillator is not an example of a sinusoidal oscillator. It is a type of relaxation oscillator that generates non-sinusoidal waveforms, such as square waves or pulses. It consists of a transistor, transformer, and a feedback network. The transistor acts as a switch, periodically blocking and unblocking the current flow through the transformer. This results in the generation of a non-sinusoidal waveform. Blocking oscillators are often used in applications such as power supplies, switching regulators, and timing circuits.

Therefore, the correct answer is option D, blocking oscillator, as it does not generate a sinusoidal waveform.