Answering Machine Detection (AMD)
Answering machine detection helps VoiceUni tell the difference between a live person and voicemail before connecting your AI agent. When detection is on, the telephony carrier classifies each answered call. Live answers can bridge to your AI agent; detected voicemail ends without bridging.
Calls classified as voicemail are typically labeled Voice Mail in your dispositions and reports.
Where to configure AMD
Location-wide defaults live under Settings → AMD. Per-campaign options live under Campaign → Advanced on outbound campaigns.
Campaign overrides apply only when you fill them in. Leave a campaign field empty to use your location default from Settings → AMD.
On Settings → AMD you can set sync or async mode, tune detection parameters, review change history, and restore a previous configuration.
On Campaign → Advanced you can turn Detect Voicemail on or off, choose whether to treat uncertain results as voicemail, and optionally override AMD mode and tuning parameters for that campaign only.
Enable or disable detection
Turn on Detect Voicemail on Campaign → Advanced for outbound campaigns that should use AMD.
An agent-level Detect Voicemail setting can also apply when enabled on the agent. If either the campaign or the agent has detection on, AMD runs for that dial.
When detection is off, answered calls are treated as live and can bridge to your AI agent without running AMD first.
Sync vs async mode
Choose the mode on Settings → AMD. Campaign → Advanced can override the mode for a single campaign.
Sync AMD waits for detection to finish before connecting. Voicemail calls do not bridge your AI agent. Use sync when you want to avoid brief AI connections on voicemail.
Async AMD may connect the customer while detection still runs in the background. Pickup can feel faster, but voicemail may briefly bridge before the call ends. If voicemail is connecting when it should not, switch to sync mode.
Treat unknown as voicemail
When the carrier cannot decide between human and machine, the result is unknown.
On Campaign → Advanced, Treat unknown as voicemail controls what happens next. When this option is on, unknown answers follow voicemail rules and do not bridge. Turn it off only if you want uncertain answers connected like a live person.
Tuning parameters
Settings → AMD holds location defaults for the four tuning fields below. Campaign → Advanced can override each value per campaign. Defaults shown are typical starting points.
Machine detection timeout (default 3 seconds, range 3–59 seconds)
Maximum time the carrier spends on detection before returning a final result. Shorter values decide faster but may produce more unknown results. Longer values wait longer before giving up.
Speech threshold (default 1200 milliseconds, range 1000–6000 milliseconds)
How long speech must last before it is treated as a greeting pattern. Increase this if long human hellos are wrongly flagged as voicemail. Decrease this if short voicemail greetings are missed, understanding that very low values can increase false machine results.
Speech end threshold (default 600 milliseconds, range 500–5000 milliseconds)
How much silence after speech ends before the carrier considers the greeting complete. Increase this to catch short voicemail greetings. Decrease cautiously if you need faster human detection, since very low values can increase false human connections.
Silence timeout (default 2000 milliseconds, range 2000–10000 milliseconds)
How long to wait on initial silence before returning unknown. Increase to wait longer on silent answers. Decrease to return unknown sooner.
After changing parameters, place a few test calls and review dispositions and recordings before rolling changes out broadly.
If voicemail is connecting when it should not
- Confirm Detect Voicemail is on for the campaign.
- Prefer Sync AMD over Async AMD.
- Turn on Treat unknown as voicemail if borderline answers should not bridge.
- Adjust speech threshold and speech end threshold using the guidance above.
- Use AMD parameter history on Settings → AMD to revert a change that made results worse.
Campaign strategies and retries
Campaign Strategies can define retry rules for voicemail and other call outcomes. Attach a strategy to a campaign when you want follow-up dials after voicemail instead of handling every outcome manually.
Provider support
Twilio, Telnyx, and SignalWire support the full set of AMD tuning options in VoiceUni.
Plivo supports machine detection timeout only. Speech and silence thresholds from Settings → AMD are not sent on Plivo outbound calls.
Sinch outbound calls do not use VoiceUni AMD settings today.
Tips
- Start from the default parameters and change one setting at a time.
- Sync mode plus Treat unknown as voicemail is the most conservative setup when you want to minimize AI connections to voicemail.
- Keep notes in the AMD history on Settings → AMD when you change values so your team can restore a known-good configuration later.