Call transfers
Handing a live call to another number or SIP destination, with the transfer method, target rules, headers, notifications and the result the application sees. Browse the feature map or configuration finder.
Availability: Next. Entries that depend on an optional feature, a role or a deployment choice name it in their own Availability line.
Features in this family
- Transfer a call from a flow
- Transfer methods (REFER, INVITE, BYE)
- Blind or notify REFER outcome
- Attended transfer through the platform
- Media path after an INVITE transfer
- Transfer target, routing pool and caller ID
- Ring time for the transfer target
- Headers and URI parameters on a transfer
- Transfer destination restrictions
- Transfer result and resume after failure
- Diagnose blocked and failed transfers
- Transfers from browser voice calls
- Transfer when the bot stops answering
- REFER target host
- Audio while a transfer is in progress
Transfer a call from a flow
A transfer step hands the caller to a phone number or SIP address, optionally after a spoken message, and continues on a success or failure path.
For: Application builders
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Flow Designer › Transfer node(transfer, method, target, targetNumber, message, playMessage, canConfirm, routingPool, callerId) | Transfer: hand off a call |
Read more:
- Set it up: Transfer: hand off a call
- How it works: 1. Choose where the transfer is configured
- Troubleshoot: 6. Verify the transfer
Related features: Transfer methods (REFER, INVITE, BYE), Transfer target, routing pool and caller ID, Transfer result and resume after failure.
Transfer methods (REFER, INVITE, BYE)
A transfer either asks the carrier to redirect the call with REFER, places a new INVITE to the target and bridges it, or ends the call with BYE for the carrier to continue.
For: Integrators, Application builders
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer node › Method(sip_refer, sip_refer_replace, sip_invite, sip_invite_bridge, sip_invite_reinvite_p2p, sip_bye) | Transfer: hand off a call |
Read more:
- Reference: Call transfer methods
- Set it up: 2. Set the target and egress route
Related features: Blind or notify REFER outcome, Attended transfer through the platform, Media path after an INVITE transfer.
Blind or notify REFER outcome
In blind mode the platform counts a REFER as done once it is sent; in notify mode it waits for the carrier's NOTIFY so a failed transfer can return to the flow.
For: Application builders, Integrators
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer node › REFER outcome mode(referOutcomeMode, blind, notify) | Transfer: hand off a call |
Read more:
- Reference: Call transfer methods
- Reference: 5. Choose a method and outcome mode
Related features: Transfer methods (REFER, INVITE, BYE), Transfer result and resume after failure.
Attended transfer through the platform
With an INVITE bridge the platform calls the target first and an AI can greet the person before the caller is connected; REFER methods offer no consultation leg.
For: Application builders, Integrators
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer action › Attended transfer(sip_invite_bridge, attendedProvider, message) | Call transfer methods |
Read more:
- Reference: Call transfer methods
- Reference: Limits
Related features: Transfer methods (REFER, INVITE, BYE), Media path after an INVITE transfer.
Media path after an INVITE transfer
After an INVITE transfer, audio either keeps flowing through the platform or the platform requests a direct peer-to-peer path on a best-effort basis.
For: Integrators
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer action › Media mode(mediaMode, gateway, p2p) | Call transfer methods |
Read more:
- Reference: Call transfer methods
Related features: Transfer methods (REFER, INVITE, BYE), Attended transfer through the platform.
Transfer target, routing pool and caller ID
The target is a number or SIP URI; a routing pool or the egress base number selects the outbound trunk, and the caller ID shown to the target follows the trunk policy.
For: Application builders, Team administrators
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer node › Target and routing pool(target, targetNumber, routingPool, callerId) | 2. Set the target and egress route |
Read more:
- Set it up: 2. Set the target and egress route
- Reference: Check outbound selection
Related features: Outbound routing pools, Transfer destination restrictions, Transfer a call from a flow.
Ring time for the transfer target
An INVITE transfer gives up when the target does not answer within the configured ring time, 30 seconds unless set otherwise.
For: Application builders
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer action › Max ring time (seconds)(maxRingTime) | Transfer: hand off a call |
Read more:
- Reference: Transfer: hand off a call
Related features: Transfer result and resume after failure.
Headers and URI parameters on a transfer
A transfer node can add SIP headers, a reason and query parameters to the target URI, within the platform header budget.
For: Integrators, Application builders
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Transfer node › SIP headers and query parameters(sipHeaders, sipQueryParams, reason) | 4. Add SIP headers |
Read more:
- Reference: 4. Add SIP headers
- Reference: Default optional-header limits
Related features: Send SIP headers on hangup and transfer, Optional SIP header budget, Transfer reason on the new call leg, Custom headers passed to carriers.
Transfer destination restrictions
Platform rules block premium-rate and service numbers, can limit transfers to allowed country codes and SIP URIs without a phone number, and a team can override them.
For: Team administrators, Deployment operators
| Level | Where to change it | Owner section |
|---|---|---|
| Platform settings | Platform configuration › Transfer restrictions(blockPremiumNumbers, premiumPrefixes, premiumPatterns, enforceAllowedCountryCodes, allowedCountryCodes, defaultDomesticCountryCode, restrictSipUriWithoutPhone) | Other Platform Settings controls |
| Team settings | Manage Team › Transfer restrictions(transferRestrictions) | Apply transfer restrictions at team scope |
Read more:
- Set it up: Apply transfer restrictions at team scope
- Reference: Other Platform Settings controls
Related features: Diagnose blocked and failed transfers, Transfer target, routing pool and caller ID.
Transfer result and resume after failure
The flow and the bot receive a result such as transferred, not reachable, not available, declined or timeout, and a failed transfer returns the caller to the conversation.
For: Application builders, Integrators
Read more:
- Reference: 5. Choose a method and outcome mode
- Set it up: 6. Verify the transfer
Related features: Blind or notify REFER outcome, Diagnose blocked and failed transfers, Ring time for the transfer target.
Diagnose blocked and failed transfers
A blocked transfer leaves a log entry with a code, for example a missing egress trunk, an exceeded header budget, a restricted destination or REFER on a browser call.
For: Application builders, Deployment operators
Read more:
- Troubleshoot: 6. Verify the transfer
- Troubleshoot: Follow the transfer method and the new
- Set it up: Transfers, hangups and keypad input
Related features: Transfer destination restrictions, Optional SIP header budget.
Transfers from browser voice calls
A flow with only browser voice entry points cannot use REFER and defaults to an INVITE transfer; validation flags a REFER method in such a flow.
Availability: Requires the Browser voice (WebRTC) feature.
For: Application builders
Read more:
- Reference: Call transfer methods
- Troubleshoot: 6. Verify the transfer
Related features: Transfer methods (REFER, INVITE, BYE).
Transfer when the bot stops answering
A flow can name a fallback target that receives the caller when the bot stays silent too long, instead of ending the call.
For: Application builders
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Flow Settings › Bot no-input give-up › Give-up transfer target(botNoInputGiveUpTransfer, routingPool) | 3. Transfer instead of ending a silent |
Read more:
- Set it up: 3. Transfer instead of ending a silent
- Reference: Give up when the bot stays silent
Related features: Give up when the bot stops responding, Transfer destination restrictions.
REFER target host
The operator sets the host name that REFER-based transfers use for the platform edge; it falls back to the edge domain when unset.
For: Deployment operators
| Level | Where to change it | Owner section |
|---|---|---|
| Services and containers | Voice and TelPro environment(REFER_TARGET_HOST, DOMAIN_TELPRO) | Voice variables |
Read more:
- Reference: Voice variables
Related features: Transfer methods (REFER, INVITE, BYE), Carrier REFER normalization.
Audio while a transfer is in progress
A system audio clip bound to the transfer trigger plays to the caller while the platform sets up the transfer.
For: Application builders
| Level | Where to change it | Owner section |
|---|---|---|
| Flow and node settings | Flow Settings › System audio triggers › Transfer(transfer) | Choose audio for App triggers |
Read more:
- Set it up: Choose audio for App triggers
Related features: Play system audio on call events, Transfer a call from a flow.