Controlling a servo with a PWM signal via Raspberry Pi GPIO pins involves generating digital signals with varying pulse widths. By adjusting the pulse width, you can set the servo's position. Raspberry Pi's GPIO pins can generate PWM signals, allowing precise control over servo motors. This method is commonly used in robotics and automation for achieving specific angular positions.

GPT-2 is a language model developed by OpenAI. It stands for "Generative Pre-trained Transformer", GPT-2 is designed for Natural Language Processing tasks and is capable of generating coherent and contextually relevant text. It's trained on a massive dataset and is known for its ability to perform tasks like text generation, text translation, paper summarization, and more. 

The LD3320 chip is a versatile speech recognition and synthesis processor. It's commonly used in applications like voice-controlled systems, smart devices, and robotics. LD3320 can recognize and process spoken language, allowing it to respond to voice commands. Additionally, it has text-to-speech capabilities, enabling it to convert text into natural-sounding speech.