#how does the outbound trunk? is it like a sip register to a certain trunk?

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main mantleBOT
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AI-generated Answer for johnnyflaco

Short answer: outbound is trunk-based INVITE routing, not SIP REGISTER.

What the docs say

  • ElevenLabs places outbound calls by sending a SIP INVITE to the termination Address (hostname or IP) you configure on the SIP trunk. You enter only a hostname/IP (no SIP URI), choose TCP or TLS for signaling, and optionally require SRTP for media. Digest auth (username/password) or ACL/IP-allowlist can be used; digest is recommended. (elevenlabs.io)
  • Signaling is over TCP/TLS; UDP transport for signaling is not available. Media (RTP) flows over UDP; if you set media encryption to Required, SRTP is used. Typical ports: 5060 (TCP) and 5061 (TLS). (elevenlabs.io)
  • Inbound to ElevenLabs uses their origination URI sip:sip.rtc.elevenlabs.io:5060;transport=tcp, while outbound from ElevenLabs uses your termination URI/Address. The docs describe digest/ACL authentication on these INVITEs and do not document any SIP REGISTER flow. (elevenlabs.io)

Related provider guides (same model: ElevenLabs sends INVITEs to your termination URI)

  • Telnyx and Plivo setup pages explicitly describe outbound from ElevenLabs to your provider via your termination URI with digest/ACL auth. (elevenlabs.io)

If you need, I can point you to the exact dashboard steps to add the trunk and set the outbound Address and auth. (elevenlabs.io)

Sources:
SIP trunking | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
SIP trunking
Telnyx SIP trunking | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation

little cedar
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how would this look like on 3cx? how to connect my agent on 3cx so it can accept calls. but also transfer calls to like a call queue at extension 104 for example

main mantleBOT
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AI-generated Answer for johnnyflaco

Short answer: use ElevenLabs SIP trunking. There isn’t a 3CX‑specific guide, but 3CX works as a standard SIP PBX. Configure a SIP trunk in ElevenLabs, point it at your 3CX SBC/FQDN, assign the number to your agent, and use the “Transfer to Human” tool to hand calls to your 3CX queue (via SIP URI with SIP REFER, or via a DID that 3CX routes to the queue).

What to set up in ElevenLabs

  • Import your SIP trunk number: Agents Platform > Phone Numbers > SIP trunking > “Import a phone number from SIP trunk.” Set Address to your 3CX hostname/IP (no sip: prefix). Choose TCP or TLS for signaling and set media encryption as needed. Then assign the number to your agent.
  • Signaling/media details to match on 3CX: SIP signaling supports TCP or TLS (recommended); RTP uses UDP; typical SIP ports are 5060 (TCP) and 5061 (TLS). ElevenLabs supports G.711 (8 kHz) and G.722 (16 kHz); ensure your PBX uses one of these or resamples.
  • Networking: allow RTP UDP ports (e.g., 10000–60000). ElevenLabs operates multiple SIP servers behind sip.rtc.elevenlabs.io; if you must IP‑allowlist, contact support.

What to do on 3CX (high‑level)

  • Create/adjust a SIP trunk that can send inbound calls to the SIP INVITE address you configure for ElevenLabs and accept outbound calls from ElevenLabs to your 3CX Address. Route your DID(s) to that trunk so calls reach the agent you assigned in ElevenLabs. The exact dial plans and routes are done in 3CX; ElevenLabs just requires standard SIP trunking per the doc above.

Transferring from the agent to a 3CX queue (e.g., extension 104)

  • Enable the “Transfer to Human” system tool on your agent and add a transfer rule. You have two interoperable options:
    1. SIP REFER to a SIP URI if your trunk allows REFER: set transfer type “SIP REFER” and Number Type “SIP URI”, e.g., sip:104@your-3cx-domain. Only SIP REFER supports SIP URI targets.
    2. Conference transfer to a phone number (DID) that 3CX routes to Queue 104: set transfer type “Conference” and Number Type “Phone” and use the E.164 DID that your 3CX maps to that queue. Note: external transfers to arbitrary numbers require using SIP trunking numbers; Twilio native numbers can only transfer to Twilio‑hosted numbers.

Notes

  • You can use non‑Twilio carriers and on‑prem PBXs via SIP trunking; that’s the supported path for setups like 3CX.

If you share your 3CX FQDN/SBC details and whether you can enable SIP REFER on your trunk, I can map the exact Transfer rule (SIP URI vs DID) against the doc’s options.

little cedar
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is there a difference between sip refer or conference transfer. or the same.. and can i just input a random did that doesnt exist?

main mantleBOT
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AI-generated Answer for johnnyflaco

  • They’re different:

    • Conference transfer: dials the destination, bridges all parties into a conference, then removes the AI so only the caller and the destination remain. Default method. (elevenlabs.io)
    • SIP REFER transfer: sends a SIP REFER to hand the existing call leg off to the destination. Works with phone numbers and SIP URIs, but only when the call is over SIP and your SIP trunk allows REFER. Only SIP REFER supports SIP URI targets. (elevenlabs.io)

  • Can you input a random DID?

    • The destination must be a valid, reachable target:
      • Phone numbers must be in E.164 format and associated with a properly configured account/provider. (elevenlabs.io)
      • SIP URIs must be valid SIP addresses and require SIP REFER. (elevenlabs.io)
    • Additionally, only SIP trunking numbers can transfer to external numbers; Twilio numbers can currently only transfer to Twilio-hosted numbers. For external transfers via Twilio, use Twilio Elastic SIP Trunking with ElevenLabs SIP trunking. (elevenlabs.io)

For SIP setup details and requirements (inbound/outbound, transport, auth, headers), see the SIP trunking docs. (elevenlabs.io)

Sources:
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation

little cedar
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is there a difference in costs? do both use the outbound trunk thats setup? wh would refer be used andw hy conference transfer? whats the different.

main mantleBOT
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AI-generated Answer for johnnyflaco

Short answer

  • Pricing: ElevenLabs does not publish different rates for conference vs SIP REFER transfers. Billing is per connected minute of the AI call; minutes are measured by the connection duration. There’s no documented surcharge by transfer method. (help.elevenlabs.io, elevenlabs.io)
  • Trunk usage: For SIP-trunked numbers, any outbound call initiated by the agent (including a transfer) is sent to your SIP trunk using the outbound “Address” you configured. (elevenlabs.io)
  • When to use which
    • Conference transfer: Default. The agent dials the destination, bridges both parties in a conference, then the AI drops so only caller and transferee remain. Works with Twilio and SIP-trunk numbers; note Twilio numbers can only transfer to other Twilio-hosted numbers. (elevenlabs.io)
    • SIP REFER transfer: Native SIP handoff using the SIP REFER method; can target phone numbers or SIP URIs. Requires the call to be over SIP and your trunk to permit REFER. Use this when your PBX/trunk supports REFER or when transferring to a SIP URI. (elevenlabs.io)

Cost nuance

  • Charges accrue only while the AI call leg is connected; after a transfer completes and the AI leg disconnects, billing stops for ElevenLabs even if the human-to-human leg continues. This follows the documented “connection duration” billing model. (help.elevenlabs.io)

Related docs for setup and behavior

  • SIP trunking setup and outbound call routing details. (elevenlabs.io)
little cedar
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yes but listen we dont have another extra number. can i just write a rnadom number and use that as DID? just for identification. because its all happening internally in our 3cx right? not pstn

main mantleBOT
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AI-generated Answer for johnnyflaco

Short answer: No. In ElevenLabs’ SIP trunking setup, the “Phone Number” field is intended to be a real E.164 number you actually connect to your PBX/carrier. The docs do not describe or support using an arbitrary/random DID as a mere identifier. (elevenlabs.io)

If you don’t have an extra PSTN number and everything is internal to 3CX, use a SIP URI target and a SIP REFER transfer instead:

  • Only SIP REFER supports transferring to a SIP URI (e.g., sip:104@your-pbx-domain) and requires that your SIP trunk allows REFER. (elevenlabs.io)
  • Destinations must be correctly formatted and actually reachable on your system; they aren’t just labels. (elevenlabs.io)

So: configure your trunk with a real E.164 number for the inbound mapping, and for internal handoffs to 3CX queues/extensions use SIP REFER to a SIP URI rather than inventing a DID. (elevenlabs.io)

Sources:
SIP trunking | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation

little cedar
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does 3cx support sip refer

main mantleBOT
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AI-generated Answer for johnnyflaco

ElevenLabs documentation does not state whether 3CX supports SIP REFER. What our docs do say is that SIP REFER transfers from an ElevenLabs agent only work when the call is using SIP and your SIP trunk allows SIP REFER; otherwise use the default Conference Transfer. (elevenlabs.io)

If you need SIP REFER specifically, please verify support in 3CX’s own documentation.

Sources:
Transfer to human | ElevenLabs Documentation

little cedar
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do i need tos etup authentication in the main trunk? or not

main mantleBOT
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AI-generated Answer for johnnyflaco

Short answer: not strictly required.

ElevenLabs SIP trunking supports two authentication modes:

  • Digest authentication (username/password) — recommended. Configure SIP Trunk Username/Password in the SIP trunk setup.
  • ACL/IP allowlisting — optional fallback if you leave credentials empty. You must allowlist ElevenLabs traffic on your side; note requests may come from different IPs behind sip.rtc.elevenlabs.io.

ElevenLabs “strongly recommends” using digest auth rather than ACL allowlisting. (elevenlabs.io)

Sources:
SIP trunking | ElevenLabs Documentation

little cedar
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3cx isnt getting any reer

main mantleBOT
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AI-generated Answer for johnnyflaco

Got it. If 3CX isn’t seeing any SIP REFER from ElevenLabs, check these required conditions:

  • The call must be running over a SIP trunk. SIP REFER transfers are only available “when using SIP protocol during the conversation.” If the call is via Twilio PSTN/WebRTC, the platform will not emit REFER. (elevenlabs.io)
  • In your agent’s Transfer to Human tool, set Transfer Type to “SIP REFER.” The default is Conference, which does not send a REFER. (elevenlabs.io)
  • Your SIP trunk must allow transfer via SIP REFER. If the trunk/pbx rejects or blocks REFER, 3CX won’t receive it. (elevenlabs.io)
  • Destination formatting must be valid:
    • Phone numbers: E.164 (e.g., +12125551234)
    • SIP URIs: sip:user@domain (only supported with SIP REFER) (elevenlabs.io)
  • Verify your SIP trunking setup is actually in use for this call (imported SIP number assigned to the agent, correct outbound Address/transport/auth). Misrouting to a non‑SIP path will prevent REFER. (elevenlabs.io)
  • If calls aren’t reaching/negotiating properly, run through SIP trunk troubleshooting (signaling to your configured Address over TCP/TLS 5060/5061, RTP allowed, auth correct). (elevenlabs.io)

If you’ve confirmed the call is over your SIP trunk and the transfer rule is set to sip_refer but you still don’t see a REFER on 3CX, please share:

  • Whether the destination is an E.164 number or a SIP URI,
  • The agent’s transfer rule configuration,
  • The SIP trunk’s transport/auth settings and the specific number that’s assigned to the agent,
    so we can pinpoint next steps using the SIP trunking and transfer tooling above. (elevenlabs.io)

Sources:
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation

little cedar
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reer

main mantleBOT
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AI-generated Answer for johnnyflaco

Do you mean SIP REFER?

On ElevenLabs, a REFER is only sent if:

  • Your call is running over a SIP trunk (not the native Twilio phone-number integration), and your SIP trunk allows SIP REFER. Only SIP mode supports REFER, and only SIP REFER can target a SIP URI. (elevenlabs.io)
  • In your agent, you’ve enabled the “Transfer to Human” tool and set the transfer rule’s Transfer Type to “SIP REFER,” with a valid destination (E.164 phone number or SIP URI). The platform then issues a SIP REFER when that rule is triggered. (elevenlabs.io)

Notes and troubleshooting on the ElevenLabs side:

  • Destination must be valid: phone numbers must be E.164; SIP URIs must be sip:user@domain. Don’t use a random DID. (elevenlabs.io)
  • For the SIP trunk itself: ElevenLabs supports digest auth or IP ACL (digest recommended), TLS for signaling is supported/recommended, and you configure the outbound Address (hostname/IP) in the SIP trunk settings. If REFER isn’t arriving, also verify your trunk auth/transport settings and that the trunk permits REFER. (elevenlabs.io)

We don’t have official 3CX-specific steps in the ElevenLabs docs; please consult 3CX’s documentation to confirm REFER support and any required settings on that side. (elevenlabs.io)

Sources:
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation

little cedar
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refer

main mantleBOT
#
AI-generated Answer for johnnyflaco

Here’s what ElevenLabs supports regarding SIP REFER:

  • ElevenLabs supports SIP REFER transfers. Configure this by adding the “Transfer to Human” system tool (transfer_to_number) and selecting transfer type “sip_refer.” SIP REFER works with both phone numbers and SIP URIs. It only works when the call is using SIP and your SIP trunk allows REFER. (elevenlabs.io)
  • Difference vs Conference transfer:
    • Conference transfer: ElevenLabs dials the destination, bridges the caller and destination in a conference, then removes the AI agent. (elevenlabs.io)
    • SIP REFER transfer: ElevenLabs issues a SIP REFER to transfer the call directly to the destination (phone number or SIP URI). Requires SIP and REFER enabled on your trunk. Only SIP REFER supports transferring to a SIP URI. (elevenlabs.io)
  • Valid destinations:
    • Phone numbers must be in E.164 format and associated with a properly configured account; do not use a random/non‑routable DID. For SIP URIs, use sip: or sips: format. (elevenlabs.io)
  • Trunk usage and authentication:
    • Outbound calls initiated by ElevenLabs are routed to your SIP trunk using your configured hostname. Authentication can be digest (recommended) or IP ACL. (elevenlabs.io)
  • Costs:
    • Documentation does not list different pricing for REFER vs conference transfers. Minutes are billed per connected call duration; LLM usage is passed through. Silent periods over 10 seconds are billed at 5% of the per‑minute rate. (elevenlabs.io)
  • Troubleshooting when “no REFER is seen”:
    • Ensure the transfer rule’s type is set to sip_refer (not conference).
    • Verify the call path is SIP trunking (not the Twilio native integration) and that your SIP trunk permits REFER. (elevenlabs.io)
    • Confirm your SIP trunk configuration (transport, auth, routing) and check firewall/ports as per the SIP trunking troubleshooting section. (elevenlabs.io)

Note: ElevenLabs documentation doesn’t provide 3CX‑specific setup or confirm whether 3CX supports SIP REFER. Please verify REFER support and routing on your PBX, then use SIP REFER transfer in the agent if supported. (elevenlabs.io)

Sources:
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
Introduction - Conversational voice AI agents | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation

little cedar
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im not seeing teh sip uri back in my 3cx logs even though its properlyset up in the transfer tool

main mantleBOT
#
AI-generated Answer for johnnyflaco

Short answer: you’ll only see a SIP URI in your PBX logs if the transfer is done via SIP REFER on a call that is actually running over your SIP trunk. By default, transfers are “Conference,” which won’t emit a SIP REFER with a SIP URI.

Checklist to fix:

  • Confirm the call is using SIP trunking, not the Twilio phone-number integration. SIP REFER transfers are only available when the conversation is over SIP and your SIP trunk allows REFER. (elevenlabs.io)
  • In your agent’s Transfer to Human tool, set:
    • Transfer Type: SIP REFER (not Conference)
    • Number Type: SIP URI
    • Destination: a valid SIP URI (e.g., sip:user@domain)
      Only SIP REFER supports transferring to a SIP URI. (elevenlabs.io)
  • Ensure your SIP trunk is configured/allowed to perform REFER transfers; otherwise the platform won’t be able to issue a SIP REFER to your PBX. (elevenlabs.io)
  • If you’re testing with Twilio phone numbers (native integration), note they can only transfer to Twilio-hosted numbers; use SIP trunking (e.g., Twilio Elastic SIP) if you need SIP URI targets. (elevenlabs.io)
  • Verify your SIP trunk settings are correctly configured (address/transport/auth) so outbound requests from ElevenLabs reach your PBX; misconfiguration can mask transfer attempts. (elevenlabs.io)

If after switching to SIP REFER + SIP URI you still don’t see it, share whether the call path is SIP trunking vs. Twilio numbers and which transfer type is selected, and we can narrow it further. (elevenlabs.io)

Sources:
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation
SIP trunking | ElevenLabs Documentation
Transfer to human | ElevenLabs Documentation

little cedar
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my 3cx is not receiving any sip refers man