Voice resource library
Practical guides and technical explainers for building and operating voice calling.
Connect your PBX or softphone over a SIP trunk, route inbound numbers to interactive call sequences, AI voice agents, or your team in the browser, review recordings and transcripts, or migrate voice traffic from your current provider.
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Start with your customer journey
SIP trunkingConnect Asterisk, FreePBX, softphones, or custom SIP infrastructure to the telephone network with digest authentication and IP access controls.Call sequencesBuild spoken greetings, keypad IVR menus, and conditional routing flows that you can test and publish in the dashboard.AI VoiceConnect a real-time AI voice agent over SIP to answer questions, run tool actions, and transfer callers to a human team.Inbound routingDirect incoming calls on your numbers to a SIP trunk, a call sequence, a ring group, or a verified forwarding number.Browser callingAnswer ring-group calls and dial outbound calls from the dashboard browser phone, without installing a softphone.Recordings and transcriptsListen to call audio and read speaker transcripts right from the call record for quality review and dispute resolution.Voice analyticsTrack answer rates, call durations, rejection reasons, and rated charges across your voice traffic.Outbound callingPlace sales, support, and notification calls with verified caller IDs, destination controls, and per-call outcome records.Voice numbersProvision local or toll-free numbers, verify outbound caller IDs, and port existing phone numbers to Bird.Contact center connectionsPair your existing contact center queues and agent desktops with Bird SIP trunking and phone numbers.WhatsApp customer conversationsFollow up after a call or deflect routine inquiries into two-way WhatsApp conversations.
Configure and operate Voice
Call logFilter and export workspace call history, inspect call durations and rated charges, and check specific rejection reasons when a call fails.Call sequencesBuild and publish call sequences for spoken greetings, keypad IVR menus, and outbound notifications with step-by-step testing.Caller IDsRegister and verify the phone numbers your workspace displays on outbound calls using an automated verification call in the dashboard.Voice destinationsEnable the countries your workspace is allowed to dial and review destination availability and fraud-risk tiers before opening traffic.Voice eventsSubscribe to call lifecycle webhooks, inspect status and timing payloads, and process updates idempotently without duplicate records.Place your first callCreate a SIP trunk, go online in the browser phone, place a test call, confirm two-way audio, and inspect the resulting call detail record.Voice overviewLearn how Bird connects your PBX, softphone, or application to the telephone network over SIP and records outcomes in the call log.PhoneGo online in the dashboard browser phone to answer ring-group calls and dial out through your SIP trunk, set your status, and pick a ringtone and audio devices.Placing callsCheck outbound prerequisites, format caller and destination numbers for SIP signaling, complete digest authentication, and understand per-minute rating.Receiving callsRoute an inbound Bird number to a SIP trunk, a call sequence, a ring group, or a verified forwarding number and verify how incoming calls were handled in the call log.Recordings and transcriptsPlay back captured call audio, read transcripts alongside call metadata, and track when post-call artifacts finish processing.Ring groupsRing your team in the browser phone when a call arrives, with ring groups you manage in the dashboard or over the API, CLI, and MCP server.SIP client setupConfigure a PBX or softphone to register and dial through a Bird SIP trunk, with step-by-step examples for Asterisk, FreePBX, Zoiper, and baresip.SIP trunksCreate a SIP trunk, enable inbound and outbound traffic, and configure IP access lists, digest credentials, and session permissions.Voice troubleshootingDiagnose common calling issues by symptom, including calls missing from the log, rejected outbound attempts, unanswered inbound routing, and one-way audio.Connect an AI voice applicationConnect a conversational AI agent over SIP, trigger backend tool actions during a live call, and transfer callers to a human agent.
Voice explained
WebRTC vs SIP, which do I use for a browser or an AI agent?See how WebRTC and SIP work together: WebRTC streams audio in the browser, SIP sets up the call on the telephone network, and browser phones combine both.What do SIP response codes mean, and why did I get a 503?Decode provisional, success, and failure SIP response codes and learn why Bird returns a generic service-unavailable response when an outbound call is refused by policy or authentication rules.What is a call detail record (CDR)?Understand what a call detail record captures for each call leg, including answer and hangup timestamps, billable duration, final status, and rated cost.What is a SIP trunk, and do I need one?Learn how a SIP trunk links your PBX, softphone, or voice application to the public telephone network for inbound and outbound calling.What is a voice AI agent, and how does it connect to the phone network?See how a real-time speech model connects to a phone call over SIP, executes tool lookups mid-conversation, and hands callers off to human support.What is a voice API?Explore how programmable call control, SIP trunking, phone numbers, and call detail records fit together to run customer voice workflows.What is SIP?Learn how SIP negotiates call setup and teardown while live audio travels on a separate media path, and why firewall rules can cause one-way audio.What is STIR/SHAKEN, and what are attestation levels A, B and C?Understand how carriers sign outbound calls to verify caller identity and what A, B, and C attestation levels signal to the receiving network.What is toll fraud, and how does Bird limit it?Protect your workspace against unauthorized international and premium-rate dialing using destination allowlists, blocked number ranges, and daily spend limits.What is VoIP?Understand how Voice over IP transports audio over packet networks and how interconnected VoIP bridges internet calls to landline and mobile numbers.Why is my call labeled Spam Likely or Scam Likely?Learn why terminating carriers and analytics engines flag outbound numbers as spam, how caller ID verification helps, and how to remediate mislabeled numbers.
Plan a Voice migration
Migrate from TwilioMove elastic SIP trunks, TwiML call flows, and phone numbers from Twilio to Bird with a staged cutover plan.Migrate from TelnyxTransition Telnyx SIP connections, call control workflows, and AI assistant traffic to Bird without dropping active numbers.Migrate from VonageReplace Vonage SIP trunks, NCCO call flows, and webhook handlers with Bird SIP trunking, call sequences, and lifecycle events.Migrate from VapiConnect your existing Vapi assistant to Bird SIP trunking and phone numbers, or move the full voice agent workflow onto Bird.Migrate from BlandRebuild Bland conversational pathways, tool calls, and SIP handoffs on Bird while keeping call recordings and transcripts intact.Migrate from BandwidthPort phone numbers, repoint SIP peers and realms, and transition inbound and outbound voice routing from Bandwidth to Bird.Migrate from PlivoSwitch Plivo Zentrunk SIP connections, XML call flows, and outbound caller IDs to Bird on a controlled schedule.
Make your next decision
Voice platformSee how SIP trunking, call sequences, AI voice agents, and global numbers work together on Bird Voice.Voice FAQsGet direct answers on SIP setup, number porting, caller ID verification, recordings, and per-minute billing.Getting startedCreate a SIP trunk, configure destination permissions, and place a verified test call in minutes.Voice pricingCheck per-minute inbound and outbound rates by country, number rental fees, and included call capabilities.Voice comparisonsCompare Bird Voice with Twilio, Telnyx, Vonage, Vapi, Bland, Bandwidth, and Plivo across SIP, AI, and pricing.
Talk to our Voice team
Move your calling workflow into production.
Start with a self-serve SIP trunk and browser test call, or talk to our team to plan number porting, PBX integration, and volume pricing.