### Answer Based on the available sources, Retell AI's backend architecture includes several key components: [(1) ]() [(2) ]() [(3) ]() Core Processing Layers: [(3) ]() - **Speech-to-Text (STT) Layer**: Converts spoken audio into text that the LLM can process - **LLM Engine**: Processes the transcribed text and generates appropriate responses - **Text-to-Speech (TTS) Layer**: Converts the LLM's text response into natural-sounding speech Voice Processing Components: [(2) ]() - **Automatic Speech Recognition (ASR) **: Converts caller speech into structured text - **Voice Activity Detection (VAD) **: Detects when the caller starts and stops speaking - **Turn-Taking Endpoints**: Determines when the AI should speak versus listen - **TTS Synthesis**: Generates natural-sounding speech with customizable tone, language, and voice persona Telephony Infrastructure: [(4) ]() [(5) ]() Retell AI supports SIP (Session Initiation Protocol) connectivity with transport methods including TCP (recommended) , UDP, and TLS [(4) ]() . The platform manages voice processing, including real-time audio transmission [(5) ]() . Integration Options: [(1) ]() Retell AI integrates with various LLMs including proprietary Retell LLM, GPT-4-series, Claude 3-series, and Google Gemini . The lan

guage setting configures the STT layer to understand and convert speech appropriately, while voice settings configure the TTS layer [(3) ]() .

​ To learn more, see the sources I considered: [[1] Voice AI](https://www.retellai.com/glossary/voice-ai) [[2] Speech Processing](https://www.retellai.com/glossary/speech-processing) [[3] custom llm - other languages](https://discord.com/channels/1186424376300679209/1242562712450367591) [[4] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[5] AI in SIP Calling & Telephony Solutions | Retell AI](https://www.retellai.com/blog/integrating-ai-with-sip-trunking-and-modern-telephony) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.