Cold transfer

The transferring party issues a redirect and drops out. In SIP this is typically a REFER, after which the caller is connected to the new destination directly. There is no consultation leg, so the transfer completes in a fraction of the time a warm transfer takes and consumes none of the receiving party’s time up front.

The trade-off is unrecoverable failure. If the destination is busy, unstaffed or misconfigured, the transferring party has already released the call and cannot intervene. Whether the caller hears a queue, a voicemail box or a disconnect is entirely determined by the receiving system.

Cold transfer suits routing to a monitored queue, to an after-hours voicemail, or to a department where the caller will restate their need anyway. It suits escalation badly: sending a frustrated caller to a human with none of the context the agent already gathered guarantees the caller repeats themselves, which is precisely the experience the agent was deployed to avoid.