What answer supervision normally means
In telephony, "answer supervision" is the signal the network sends back to the originating side indicating the far end has picked up — this is what triggers billing to start on a call. Correct answer supervision means billing genuinely reflects when the call was actually answered.
What "false" answer supervision means
False answer supervision (FAS) is when that answer signal is sent, and billing starts, even though the call was not genuinely answered by a person — for example, still ringing, going to an intercept message, or not connecting at all, while still being billed as if it had connected. It's called out specifically as a wholesale-termination risk because it's a billing-integrity issue as much as a technical one: a route with FAS can look artificially "successful" in raw connection statistics while actually costing more per genuinely-answered call than its headline rate suggests.
Why it happens more on some routes than others
FAS is more of a risk on routes with longer or less-direct interconnect paths — where a call passes through more intermediate carriers, there's more opportunity for an intermediate hop to send a premature or incorrect answer signal, whether through misconfiguration or, less charitably, to inflate billed minutes. Direct/tier-1 routes with fewer intermediate hops are generally lower-risk, though "generally lower-risk" is not the same as "guaranteed free of it" — see the note on claims below.
How FAS affects your costs
If billing starts on calls that weren't genuinely answered, your actual cost per real (human-answered) call is higher than the advertised per-minute rate implies — you're effectively paying for some volume of calls that never really connected. This is separate from, and can compound with, the billing-increment effects covered in the billing increment calculator.
How to test a route for answer supervision
- Place a controlled sample of real calls to numbers where you can independently confirm whether they were actually answered (e.g. numbers you control, or numbers you can call in parallel by another means).
- Compare the carrier's reported "answered" status and billed duration against what actually happened on the call.
- Look for a pattern of billed calls where you have reason to believe the far end never picked up, or picked up meaningfully later than billing indicates.
- Repeat across a large enough sample and enough destinations to distinguish a real pattern from normal call-outcome variance.
This is exactly the kind of check a route test is meant to surface before you commit production volume — see also how to test a VoIP route for the broader testing checklist (ASR, ACD, PDD, audio quality, CLI), which answer-supervision testing complements rather than replaces.
What not to claim — and what CallCenterBoost does not claim
Neither CallCenterBoost nor any wholesale provider should advertise a route as "100% FAS-free" unless that specific claim is actually backed by route data and, where relevant, carrier contract terms — a claim like that made without real evidence is exactly the kind of unsupported route-quality statement this Knowledge Hub avoids. The honest, useful framing is procedural, not promotional: test routes for answer supervision before committing production traffic, the same way you would test ASR, ACD and PDD.