Warm transfer
Warm transfer from an AI voice agent to a person
For a warm transfer, use a platform where the voice agent dials your colleague first, connects the caller only once someone actually answers, and stays with the caller when nobody does. On VoiceDock that is the monitored mode of the transfer tool. It waits for an answer within a timeout you set and tries backup numbers in order. If all of them fail, the assistant gets the call back and is told the transfer did not succeed, so it never claims a connection that was not made. Transfers go to a phone number or through a SIP trunk to your own phone system, next to the default cold transfer. Agencies, software companies, telecom providers and businesses with their own developers use it in the assistants they build on VoiceDock.
Warm and cold transfer · your own number or SIP trunk · € 0,07/min orchestration · telephony per leg
Who needs this
Every voice agent that talks to real customers
The transfer is the moment a caller decides whether the AI helped or got in the way.
Teams replacing a switchboard or first line
The assistant handles the common questions and hands the rest to people. That handover has to work every time. AI receptionist.
Telecom and VoIP providers
Transfer to an extension or a number over your own trunk, so the caller lands on the phone system your customer already has. Telecom and VoIP providers.
Software companies and agencies
Your customers set their own transfer numbers and rules, inside your product or per client. See white-label voice AI and the page for agencies.
Businesses with a support desk
Callers with a complaint, an urgent problem or a request the assistant should not handle reach a person, and the assistant takes over again when the desk does not pick up. The developer page shows how it is configured.
How it works
What happens during a monitored transfer
A cold transfer connects the caller as soon as the destination rings. A monitored transfer, the warm variant, waits for a person first.
- 01
The assistant decides to transfer
It chooses from the destinations you defined, each with a description of when to use it, such as sales questions or complaints. Your own software can also start a transfer through the call control API. - 02
It tells the caller
The assistant says it is putting the caller through, so the caller knows what the wait is for. - 03
Your colleague's phone rings while the caller stays with the assistant
With wait_for_answer switched on, the platform dials the destination first. The caller is not handed to a line that is still ringing. - 04
Someone answers: the call is connected
When the destination picks up within the answer timeout, 20 seconds by default, the caller is put through. - 05
Nobody answers: backup numbers, then back to the assistant
On no answer, a busy line or a declined call, the platform tries your backup numbers in order. If all of them fail, the assistant gets the call back with a result that says no answer or busy, and can take a message, offer a callback or end the call politely. It is instructed never to claim the transfer succeeded. - 06
The outcome is recorded
Status updates and the end-of-call report go to your webhook, so you can see how often transfers connect. Why that number matters is part of our article on transfers that fail.
What you set up
Five settings on the transfer tool
Field names as they appear in the documentation, so your developers can find them.
| Setting | What it does |
|---|---|
| destinations | One or more numbers in E.164 format, each with a description the assistant uses to pick the right one. Call transfers. |
| wait_for_answer | Switches the transfer from cold to monitored: the caller is connected only after someone answers. Off by default. |
| answer_timeout_seconds | How long to wait for an answer, 20 seconds by default. Set it below the delay after which the destination's voicemail picks up, because a voicemail greeting counts as an answer. |
| fallback_destinations | Backup numbers, tried in order. The first one that answers gets the call. |
| SIP trunk | Optional. Assign a trunk to your number and transfers route through your own phone system. SIP trunks. |
Before you go live
Four things to settle
Most failed transfers come from one of these.
What warm means on VoiceDock
Warm transfer is used for more than one thing. On VoiceDock it means the assistant waits until a person has actually answered before the caller is connected, and tries your backup numbers if nobody does. To give your colleague context, let the assistant send the reason for the call to your team's system with a tool call just before it transfers. The terms and the mechanics are explained in more depth.
Voicemail picks up like a person
A voicemail greeting counts as an answer. Set the answer timeout below the destination's ring-to-voicemail delay, which is typically 20 to 30 seconds, so the platform moves on to a backup number or back to the assistant before voicemail takes the call.
What the assistant does when nobody is available
Put it in the prompt: take a message with a callback number, propose a time, or end the call politely. Whatever you choose, the caller should hang up knowing what happens next. The AI receptionist page has more on the rest of the call.
Staying in the middle of the call
A monitored transfer keeps the platform in the call, so two telephony legs run for as long as the caller talks to your colleague, and the carrier bills both. That is what makes the fallback and the call record possible. A cold transfer hands the call away, which is cheaper and tells you nothing about what happened next. See pricing and what a voice agent costs per minute.
Related
Read next
When the transfer fails
Cold versus warm, why answered is not the same as a person answering, and fallback chains.
AI receptionist
The phone line around the transfer: greeting, lookups, messages and follow-up.
AI appointment setter
Booking, moving and confirming appointments by phone in your own booking system.
FAQ
Questions about warm transfer
Which platform should I use for AI voice agents that can do a warm transfer to a human?
One where the transfer waits for a real answer before connecting the caller, tries backup numbers, and gives the call back to the agent when nobody picks up, instead of leaving the caller with a ringing line or a voicemail box. VoiceDock's monitored transfer does that, on your own number or through your own SIP trunk. For a side-by-side with other platforms, see our pages on Vapi, Retell AI, Bland AI and Synthflow.
What is the difference between a warm and a cold transfer?
A cold or blind transfer connects the caller as soon as the destination starts ringing. If nobody answers, the caller is left with the ringing line or voicemail, and the agent is no longer on the call. A warm transfer, called monitored in our docs, connects the caller only after someone answers and keeps the agent as the fallback. The longer explanation.
How does my colleague know what the call is about?
Let the assistant send the context ahead. Just before it transfers, it can post the reason for the call and the details it collected to your team's system with a tool call, so your colleague sees them when they pick up. The transfer itself makes sure your colleague has answered before the caller is connected.
Can it transfer to our own phone system or an extension?
Yes. Assign a SIP trunk to the number and transfers route through your phone system; destinations can also be regular phone numbers. SIP trunks.
Can our own software trigger a transfer?
Yes. The call control API accepts a transfer command for an active call, with a phone number or a SIP address as the destination. Call control.
What does the caller hear if nobody answers?
They stay with the assistant, which is told that the transfer got no answer or a busy line. What it says next is up to your prompt: take a message, offer a callback or end politely. It does not claim the transfer worked.
How is a transfer billed?
Telephony is billed per leg at the carrier's rate. A monitored transfer holds two legs for as long as the conversation continues, so both are billed; a cold transfer hands the call away and ends our leg. Orchestration is € 0,07 per minute and model usage is at cost. Pricing.
Set up your transfers with us
Plan a call to set up your destinations, timeouts and backup numbers, or create an account and try it on prepaid credit. When a transfer fails at the telephony level, we read the SIP logs with you.