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Introduction

You can dial-in to your Pipecat bots, and have them dial-out too, across both PSTN and SIP. The technical implementation will depend on your chosen transport and phone number vendor; each will likely have their own methods and events to consider.

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Key Terms

PSTN (Public Switched Telephone Network): The traditional phone network consisting of physical phone lines, cables, and transmission links. PSTN operates on a one-user-per-line basis. SIP (Session Initiation Protocol): A signaling protocol used for voice and video calls over IP networks. SIP can handle multiple users per line and enables advanced call control features like transfers, forwarding, and multi-party calls.

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Telephony Connection Options

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WebSocket Connections

Best for: Simple telephony workflows and quick prototypes
  • How it works: Real-time audio streaming over WebSocket connections
  • Call control: Basic, managed by the telephony provider
  • Supported providers: Twilio, Telnyx, Plivo, Exotel
  • Limitations: No advanced call center features like transfers or reconnects
When to use:
  • Simple inbound/outbound calling
  • Integration with existing Twilio Studio or Flex workflows
  • Quick setup with minimal configuration

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WebRTC Connections

Best for: When connecting web clients to telephony systems or for more complex transfer scenarios
  • How it works: Peer-to-peer real-time communication optimized for varying network conditions
  • Call control: Advanced, includes track-level control
  • Supported providers: Daily (with PSTN integration)
  • Benefits: Designed for scale, handles network variations gracefully
When to use:
  • When connecting web or mobile clients to telephony systems
  • Applications requiring high-quality audio/video
  • Users on devices with varying network conditions

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SIP Connections

Best for: Enterprise telephony and advanced call control scenarios
  • How it works: Industry-standard protocol for voice/video calls over IP
  • Call control: Full control, including transfers, forwarding, multi-party, etc.
  • Integration: Works with legacy call centers and telephony systems
  • Vendor flexibility: Supports multiple telephony vendors without platform-specific code
When to use:
  • Multi-agent or multi-party calls
  • Integration with legacy call centers
  • Advanced features: warm transfers, agent assist, call forwarding
  • Enterprise telephony requirements
Multiple providers: You can configure your Pipecat bots to handle multiple vendors simultaneously. For example, use both Daily and Twilio as phone number providers concurrently.

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Telephony Provider Options

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Daily PSTN (WebRTC)

Direct PSTN connectivity through Daily’s platform with WebRTC transport.
  • Setup: Purchase phone numbers directly through Daily
  • Transport: WebRTC for optimal audio quality
  • Use case: A range of use cases, from simple to complex including cold and warm transfers
Daily PSTN Guide →

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Daily + SIP Integration

Combine Daily’s WebRTC transport with SIP-based telephony providers.
  • Setup: Use existing Twilio numbers with Daily transport
  • Transport: WebRTC with SIP forwarding
  • Use case: Leverage existing Twilio workflows with Daily’s transport benefits
Daily + Twilio SIP Guide →

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WebSocket Providers

Direct integration with telephony providers using WebSocket connections.

Twilio WebSocket

Media Streams integration with Twilio’s telephony platform

Telnyx WebSocket

Real-time media streaming with Telnyx services

Plivo WebSocket

Voice streaming API integration with Plivo

Exotel WebSocket

WebSocket integration with Exotel telephony platform

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Next Steps

Choose the telephony option that best fits your use case and follow the corresponding guide. Each option provides complete setup instructions and example code to get you started quickly.