<!-- Canonical: https://www.agentlist.io/transports/pstn-sip -->

Transport — Realtime media

# PSTN / SIP

Low-latency voice and media pipes. Phone calls — telephony carriers terminate agent voice onto the public phone network. [www.twilio.com ↗](https://www.twilio.com/)

MIX

## Who speaks it

-   06[voice agents](https://www.agentlist.io/categories/voice-agent)
-   02[AI employees](https://www.agentlist.io/categories/digital-employee)

BY

## Vendors (8)

-   [Bland AI](https://www.agentlist.io/ai/bland)
-   [Decagon](https://www.agentlist.io/ai/decagon)
-   [Deepgram](https://www.agentlist.io/ai/deepgram)
-   [ElevenLabs](https://www.agentlist.io/ai/elevenlabs)
-   [Retell AI](https://www.agentlist.io/ai/retell)
-   [Sierra](https://www.agentlist.io/ai/sierra)
-   [Synthflow](https://www.agentlist.io/ai/synthflow)
-   [Vapi](https://www.agentlist.io/ai/vapi)

MATRIX

## Agents on this wire (8)

[Sierra Sierra · digital-employee chat/voice/api · cloud · Outcome-based (per resolved conversation); enterprise contracts](https://www.agentlist.io/systems/sierra)

[Decagon Decagon · digital-employee chat/voice/api · cloud · Enterprise; per-resolution or per-conversation pricing — quote-based](https://www.agentlist.io/systems/decagon)

[Vapi Vapi · voice-agent api/voice · cloud · Usage-based: ~$0.05/min platform fee + model/telephony costs](https://www.agentlist.io/systems/vapi)

[Bland AI Bland AI · voice-agent api/voice · cloud · Usage-based per-minute; enterprise plans](https://www.agentlist.io/systems/bland)

[Retell AI Retell AI · voice-agent api/voice · cloud · Usage-based (~$0.07+/min); enterprise plans](https://www.agentlist.io/systems/retell)

[Synthflow Synthflow · voice-agent api/voice · cloud · Plans from ~$29/mo; per-minute overages](https://www.agentlist.io/systems/synthflow)

[ElevenLabs Agents ElevenLabs · voice-agent api/voice · cloud · Included in ElevenLabs plans; per-minute credits](https://www.agentlist.io/systems/elevenlabs-agents)

Extended matrix — 1 more

80/20 preview

TABLE

## Transport table

| Agent | Vendor | Category |
| --- | --- | --- |
| SierraSierra is the customer-service AI employee for large consumer brands: it resolves support conversations across chat and voice, takes actions in business systems, and bills on outcomes. | Sierra | digital-employee |
| DecagonDecagon builds autonomous customer-support agents that resolve chats, emails, and calls for mid-market and enterprise brands, with engineering-grade tooling for the ops team behind them. | Decagon | digital-employee |
| VapiVapi is the developer platform for voice agents: API-first orchestration of STT, LLM, TTS, and telephony so you can put an agent on a phone number in minutes — and swap every layer. | Vapi | voice-agent |
| Bland AIBland AI is the enterprise phone-agent platform: autonomous inbound/outbound calls at scale with an emphasis on security, compliance, and call-center-grade throughput. | Bland AI | voice-agent |
| Retell AIRetell AI is a voice-agent platform focused on production call quality: fine-grained latency tuning, interruption handling, and both API and no-code agent building for phone agents. | Retell AI | voice-agent |
| SynthflowSynthflow is the no-code voice-agent product: agencies and SMBs build receptionist, intake, and outbound agents from templates without touching telephony or APIs. | Synthflow | voice-agent |
| ElevenLabs AgentsElevenLabs Agents is the voice agent platform built on the industry's best-known TTS: conversational agents with top-tier voices, phone and web deployment, and model-agnostic reasoning. | ElevenLabs | voice-agent |

KIND

## More realtime media

-   [WebRTC](https://www.agentlist.io/transports/webrtc)

---

Source: [PSTN / SIP — agent transport | agentlist.io](https://www.agentlist.io/transports/pstn-sip). This is the public page rendered as Markdown; interactive controls require the website.