Conceptual Guides

  • Call Flow: The various stages of a call and how they interact.
  • Numbers: Numbers are a key part of using the Vonage Voice API. This guide covers number formatting, outgoing caller IDs and incoming call numbers.
  • Endpoints: When connecting a call, you can connect to another phone number, a sip endpoint or a websocket. These are known as endpoints.
  • Text to Speech: Using our Text-To-Speech engine, you can play machine-generated speech to your callers
  • Customizing Spoken Text: Use Speech Synthesis Markup Language (SSML) to control how text-to-speech is read out
  • Speech to Text: Capture user input by converting user speech to text form during a call.
  • DTMF: Capture user input by detecting DTMF tones (button presses) during a call.
  • Call Recording and Transcription: Recording audio input from a caller or recording the conversation between two callers.
  • WebSockets: You can connect the audio of a call to a WebSocket to work with it in real time.
  • PSTN Branded Calling [Beta]: Vonage PSTN Branded Calling allows companies to display their company name, logo, and call purpose to the recipient (end user) of the PSTN phone call.
  • Advanced Machine Detection: Using our Text-To-Speech engine, you can play machine-generated speech to your callers
  • Regions: Recording audio input from a caller or recording the conversation between two callers.
  • Fraud Prevention: Protect your Voice API applications from fraud
  • Programmable SIP: Learn how to integrate your existing SIP Infrastructure with the Vonage Communications Platform.
  • Calls Per Second (CPS) Limit: How the Calls Per Second (CPS) limit works and how to design your system to stay within it.
  • Understanding Voice Automation: Understanding Voice Automation covering Simple IVR, Advanced IVR and Voice AI Agent
  • Troubleshooting: A few things to look for if you are experiencing problems with the Voice API.

In-App Calling

  • In-App Calling: Learn how In-App Calling works within the Voice API, including the lifecycle of a call, signaling, media flow, and event handling.

Best Practices

  • Media Controls: Control mute, earmuff, DTMF, and noise suppression during a call
  • Push Notifications: Configure iOS PushKit and Android FCM for inbound call delivery
  • Reconnection and Network Resilience: Handle media disconnect, reconnecting, and reconnection success flows
  • Call Transfer: Handle call transfer events and conversationId updates
  • Managing Call Hold: Learn how to implement call hold functionality in your iOS and Android applications using the Vonage Voice Client SDK.
  • ProGuard Rules: Configure ProGuard and R8 rules for Android apps using the Vonage Voice Client SDK.
  • Recover Pending Call Invites: Recover a pending inbound call invite after a page refresh or app restart by passing the previous session ID to createSession
  • Peer Connection Events: Access the RTCPeerConnection before ICE gathering begins to observe WebRTC lifecycle events
  • Logging and Diagnostics: Configure SDK log levels and custom loggers for debugging and monitoring

Audio Output for Calls

SDK Documentation