Numbers & trunks
IVRAlso known as Interactive Voice Response, Auto attendant
Definition
IVR (Interactive Voice Response) is a phone system feature that answers calls automatically, plays recorded or synthesised prompts, and lets callers choose options by pressing keys (DTMF) or speaking. It routes callers to the right extension, queue or self-service function, such as balance checks, without a human operator.
How an IVR works
A call arrives on a DID that the PBX routes to the IVR. The IVR answers, plays a greeting (“Press 1 for sales…”), and waits for input. Key presses arrive as DTMF, usually RFC 4733 events; speech input uses automatic speech recognition. Based on the input, the IVR transfers to an extension or queue, plays information, or runs a script against a database.
- Simple auto attendant: a single menu with transfers.
- Multi-level IVR: nested menus, time-of-day and holiday routing.
- Self-service IVR: looks up accounts, balances or order status via APIs.
- Conversational IVR: natural-language speech and AI agents.
Design tips
- Keep menus to four or five options and no more than two or three levels.
- Put the most common option first and always offer a way to reach a person.
- Record prompts in a consistent voice and keep them short.
- Test DTMF on every trunk type; a method mismatch makes the IVR “deaf”.
IVRs over mobile lines
An IVR is also a source of insight: which options callers choose, and where they hang up, show how well the menu serves them and where it needs simplifying.
Calls arriving through a GSM gateway can land on an IVR exactly like calls from a SIP trunk, provided DTMF from the mobile side is detected and passed as events. GSMCalls forwards inbound mobile calls over SIP to your PBX’s IVR or queues; see how it works.
Frequently asked questions
What is the difference between an IVR and an auto attendant?
An auto attendant is a simple IVR that just transfers calls. The term IVR also covers self-service and database-driven applications.
Why does my IVR not respond to key presses?
Usually a DTMF mismatch: one side sends in-band tones or SIP INFO while the other expects RFC 4733 events, or the payload type differs.
Can an IVR use speech instead of keypad input?
Yes. Modern IVRs use speech recognition and natural-language understanding, often alongside DTMF as a fallback.