# Keep your phone system. Connect it to more. Connect your PBX, softphone or SIP application to Bird. Keep your call-handling logic, with inbound and outbound calling, caller identity and call records in one workspace. [Start for Free](/dashboard/signup?returnTo=%2Fdashboard%2Fw%2Fvoice%2Fsip-trunks) [Contact sales](/demo?product=voice-sip) ## Set up with your agent [Read the agent setup guide](/docs/ai/set-up-your-agent) Copy this prompt into your coding agent: ```text Bird connects customer communications, data and automation. Help me build with Bird using my coding agent. 1. Read https://bird.com/docs/ai/set-up-your-agent.md and follow its setup workflow for this client. Use an existing connected Bird MCP server or signed-in CLI when available. 2. Read the product guide for the task I want to complete and inspect my existing integration. Identify the workspace, available operations and required setup. 3. Help me complete a first example for the product and destination I choose. Follow the operation through to its actual result, explain any uncertainty, and help me choose the next step. First task: Inspect my PBX or softphone, trunk configuration, caller identity and enabled destinations. Prepare the smallest SIP connection test. First use the connected Bird MCP server or signed-in CLI for a read-only inventory. Discover the available tools and read their schemas or help; do not invent call-control operations. If neither surface is available, follow https://bird.com/docs/ai/set-up-your-agent.md. Read the linked guides through their .md alternatives. Present the exact target and configuration before changing routing, placing calls, recording audio, purchasing numbers or submitting a port. Obtain my approval for those actions. Use this Bird page as the starting context: https://bird.com/products/voice/sip-trunking Read its Markdown alternative and linked guides. Keep the first example relevant to this page and the customer outcome I choose. Preserve the supplied campaign context when following Bird signup or sales links. ``` The path of a call Your phone system PBX, softphone or SIP application Bird SIP trunk Authenticate identity and destination Customer’s phone Connect signaling and two-way audio Your Bird number An incoming customer call Inbound trunk Deliver to your configured gateway Answer with the handling you designed One place to investigate Follow both directions in call records and events. Illustrative connection paths. Configure and test both call directions. Trusted every day by teams that build world-class software [Read more customer stories](/customers) - [Airwallex](/customers/airwallex) - [Glovo](/customers/glovo) - [Zillow](/customers/zillow) - Uber - [Binance](/customers/binance) - Adobe - Meta - PayPal - Pinterest - Square - [Al Jazeera](/customers/aljazeera) - [Aramex](/customers/aramex) - [Bazaar Technologies](/customers/bazaar) - [ComparaOnline](/customers/compara) - [Emma](/customers/emma) ## How does SIP trunking work? Your phone system sends a call request to its Bird trunk address. Bird authenticates the request, checks whether the call is allowed and connects the carrier leg. SIP establishes the session; media carries the conversation. Both paths need to work for a successful call. ### Keep your application Use a PBX, a desktop softphone or a SIP-capable application. Read the connection details from the trunk, then match transport, authentication and media settings in your client. ### Separate the directions Outbound calling lets your equipment place calls through Bird. Inbound calling delivers calls from your numbers to the gateways you configure. Turn on and test each direction deliberately. ## Choose who can place calls. Give each site or application the trunk configuration it needs. Use IP allow lists for known equipment, allowed keys for authenticated clients, or short-lived session credentials for browser and temporary clients. A trunk address on its own grants no calling permission. - **01** Prepare your identity: Use an eligible Bird number or verify a number you control. The presented caller identity and the destination both participate in the admission checks. - **02** Enable your markets: Turn on the destination countries you need and review current rates. A country being available is different from your workspace enabling it, and neither guarantees every number will connect. ## From a failed ring to a useful answer. Inspect the call’s status, final SIP response and any recorded rejection reason. A credential failure may happen before a call record exists; a destination or capacity refusal belongs to a different part of the path. Diagnose the stage before retrying. ### Start with a real test Place a call to a number your team controls. Check audio in both directions, keypad tones and clean hangup before routing customer traffic. ### Keep capacity explicit Plan concurrent calls and calling rate separately. Compare your workload with the applicable account limits and arrange capacity before a larger launch. ## Questions about SIP trunking ### Do I need to replace my PBX? No. SIP trunking connects a compatible phone system to Bird. Match the trunk’s supported transport, authentication and media settings to the client you use. ### Can one trunk handle incoming and outgoing calls? Yes. Configure each direction separately. Incoming calls also need an inbound-capable number pointed at the trunk and a delivery gateway. ### Can an AI voice application connect over SIP? Yes, when its runtime can handle both the SIP signaling and audio connection. The conversational application controls its speech, model and business actions; Bird carries the telephone connection. ### What happens if I disable inbound calling? Numbers pointing at that trunk return to a rejecting route. Re-enabling the trunk does not restore their previous bindings; review the numbers before resuming traffic. ### Does Bird Voice carry emergency calls? Bird Voice does not carry emergency calls. Use a phone service designed for that requirement. ## Build the next part of your calling path [SIP trunking guide](/docs/guides/voice/sip-trunks) Follow the setup, requirements and operational checks. [Inbound routing](/products/voice/inbound-routing) Connect each number to your phone system, forwarding target or call sequence. [Browser calling](/products/voice/browser-calling) Place an outbound call from your workspace with a browser phone and your SIP trunk. [Voice pricing](/pricing/voice) Review published destination rates and relevant call components. ## Connect your first trunk. Prepare your trunk, caller identity and destinations. Test your PBX or softphone with a number your team controls before moving customer traffic. [Read the SIP guide](/docs/guides/voice/sip-trunks) ## Related resources - [Voice overview](/docs/guides/voice/overview) (docs) - [What is a voice API?](/explained/voice/what-is-a-voice-api) (answer) - [Voice](/products/voice) (product) [Get an implementation brief](/learn/workspace?topic=voice)