Glossary · Hosting & DevOps
SignalWire
Overview
What SignalWire is
SignalWire is a programmable communications platform that exposes voice, messaging, video, and SIP through developer APIs. It was founded in 2017 by the core engineers behind FreeSWITCH, the open-source telephony engine, and is built on its own real-time media stack rather than reselling another provider's network.
It occupies the same category as CPaaS providers such as Twilio and Telnyx, offering carrier-grade calling, phone numbers, and SIP trunking. More recently it has added a voice-AI SDK to help teams connect AI agents to live phone calls.
How SignalWire works
Developers provision phone numbers and connect to the PSTN, WebRTC, or SIP endpoints, then control call behavior programmatically through SignalWire's APIs and SDKs. Because it runs its own media engine, it handles low-latency audio, transcription, and routing close to where calls are processed.
For voice AI, SignalWire provides an SDK that bridges a call's audio to speech recognition, a language model, and text-to-speech, and back to the caller. This lets an AI agent answer, listen, respond, and transfer to a human on the same telephony fabric.
Where it fits in a voice-AI stack
SignalWire sits at the telephony and transport layer of a voice stack, the part that connects an AI agent to real phone numbers, SIP trunks, and the carrier network. Orchestration platforms like Vapi or custom pipelines built on LiveKit often rely on a provider like SignalWire, Twilio, or Telnyx to carry the actual call.
Choose it when you want programmable, carrier-grade communications with SIP flexibility and an option to run voice AI on the same platform. Compare pricing, number coverage, and SIP features against Twilio and Telnyx for your region.
Where we use it
Related Zen in Tech services
How our team puts SignalWire to work in real projects.
FAQ
SignalWire — common questions
What is SignalWire used for?
SignalWire is used to build and run programmable voice, messaging, video, and SIP applications. Typical uses include cloud phone systems, SIP trunking, contact-center routing, and connecting AI voice agents to the public phone network.
How does SignalWire compare to Twilio?
Both offer programmable communications APIs, but SignalWire runs its own media engine (built by FreeSWITCH creators) and emphasizes SIP flexibility and cost efficiency. Twilio has a larger ecosystem and product breadth; compare pricing, coverage, and features for your workload.
Can SignalWire power AI voice agents?
Yes. SignalWire provides a voice-AI SDK plus its telephony layer, so you can connect a call's audio to speech recognition, a language model, and text-to-speech. It handles the phone-network side while your logic drives the conversation.
Need SignalWire done right?
Book a free consultation and we’ll map the fastest, most cost-effective path for your project.
Knowledge hub
From our knowledge hub
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