### Answer For handling engaged lines and custom voicemail scenarios during call transfers, consider using warm transfer instead of cold transfer, as it provides more control over detection and handling. [(1) ]() ## Warm Transfer Configuration for Your Scenario With warm transfer, you can enable these settings: - **Enable human detection**: When enabled, the agent will check if a human is present after the transfer target answers. The original caller will only be connected once a human is detected. - **Auto-greet**: If enabled, the agent will immediately say "Hello" when the transfer target picks up. This encourages a response, increasing the likelihood of detecting a human. - **Agent detection timeout**: The maximum amount of time the AI agent will wait to determine whether the transfer target is a human. The caller is connected only if human detection succeeds within this timeframe. Otherwise, the transfer is marked as failed. The default timeout is 30 seconds. ## Handling Custom Human-Sounding Voicemails The human detection feature combined with auto-greet helps distinguish between actual humans and recorded messages. The agent says "Hello" and waits for a response—a recording won't respond dynamically, which helps the detection logic identify it's not a live human. ## Ring Duration Setting There's a global

ring_duration_ms

setting that controls how long the phone rings before giving up. Default is 30000 ms (30 seconds) , with a valid range of 5000-90000 ms. [(2) ]() However, this is a global setting. A community member noted that having separate ring duration settings for outbound calls vs. transfers would be beneficial, and this has been submitted as a feature request. [(3) ](

679209/1448474483156324373) ## Transition on Failure The Call Transfer node has a pre-populated edge for when transfer fails—you can connect that to a node to handle transfer failure scenarios (like engaged lines or voicemail detection failures) . [(1) ]()

​ To learn more, see the sources I considered: [[1] Call Transfer Node](https://docs.retellai.com/build/conversation-flow/call-transfer-node) [[2] Create Voice Agent](https://docs.retellai.com/api-references/create-agent) [[3] Failed Transfers](https://discord.com/channels/1186424376300679209/1448474483156324373) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.