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Glossary · Voice technology

What is Answering machine?

  • Also called: answerphone, answer machine

Reviewed by Sujan ThapaliyaLast updated

Definition

An answering machine records messages from callers when nobody picks up. Originally a device attached to the line, the function now lives almost entirely in the network as voicemail — but the term survives, particularly in the phrase answering machine detection.
The three STIR/SHAKEN attestation levels, which underpin how answering machine behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, answering machine included.

In practice

How answering machine actually works

The distinction still matters technically. A physical machine answers the line, which means the call connects and billing starts; network voicemail answers within the network, which is why a call to a busy mobile can reach a mailbox without ever completing to a handset.

For outbound dialling the difference is invisible: both produce a greeting followed by a beep, which is exactly what answering machine detection is listening for.

The phrase persists in the industry because the acronym AMD does, and renaming it would break every dialer setting screen in existence.

The distinction still matters for one practical reason: a physical machine answers the line, so the call connects and billing starts, while network voicemail can answer without the handset ever being reached. On a per-minute plan that difference is small; across a campaign of tens of thousands of calls it is not.

Worked example

Both a physical machine and network voicemail play a greeting and a beep, so detection cannot tell them apart — and does not need to. The difference matters for billing, not for dialling.

Answering machine: common questions

Is an answering machine the same as voicemail?
Functionally yes, structurally no. An answering machine is a device on the line; voicemail is a service in the network. Almost everything called an answering machine today is actually voicemail.
Why do dialers still say 'answering machine detection'?
Because the term predates network voicemail and stuck. The detection does not care which is answering — it is listening for a greeting rather than a person, and both sound the same.
Can a caller tell the difference?
Rarely. Both play a greeting and a beep. The only reliable tell is timing: network voicemail often answers faster, particularly when the handset is switched off.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

See answering machine in the product

A voicemail drop leaves a pre-recorded message in a contact's mailbox during an outbound call, so the rep moves to the next number instead of speaking the same 20 seconds again. One keystroke, or automatically when answering-machine detection hears a greeting.

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