The single biggest thing standing between a business and AI on the phones is usually four words: "but our phone system." You've invested in a PBX, trained your team on it, wired your numbers and extensions through it. The idea that adopting AI means tearing all that out and migrating to something new is enough to stop the conversation before it starts.
So Mihu doesn't ask you to. Instead of replacing your phone system, it joins it — registering as just another extension over SIP, exactly like adding a new softphone. It answers the calls you point at it, handles them with AI, and transfers or routes callers straight back into your existing extensions and departments. Your PBX stays; the intelligence is added on top.
The rip-and-replace fear
Replacing a phone system is a genuine project: new hardware or platform, number porting, re-training, downtime risk, and a migration that has to go perfectly because the phones can't stop ringing while you do it. For most teams the calculation is simple — the upside of AI has to be enormous to justify that kind of disruption, so they wait.
The good news is that the choice between "keep my PBX" and "use AI" was always a false one. They're not mutually exclusive. An AI agent that speaks the same protocol your PBX already speaks can simply live inside it, no migration required.
Mihu as an extension
At its simplest: Mihu becomes an extension on your PBX. You create an extension the way you would for any new employee's softphone, give Mihu its SIP credentials, and from that moment Mihu can answer calls on your system. To your PBX, it's just another endpoint — one that happens to be answered by an AI agent that never sleeps, never puts anyone on hold, and speaks your customers' languages.
Because it's a standard extension, everything your PBX already does still applies. You decide which calls reach Mihu — a dedicated number, the main line's auto-attendant, an overflow queue, after-hours routing — using the same call-flow tools you use today. Nothing about your existing setup has to change to make room for it.
How it works
That last step is what makes it more than a standalone answering machine. Mihu doesn't trap callers in an AI dead-end — when a human is the right next step, it hands the call straight back into your PBX, to the extension or team that should take it.
What it can route to
Once Mihu has understood what a caller needs, it can send them wherever your setup requires:
A smart front door to your existing extensions
Point your main line at Mihu and it becomes a Smart IVR for your whole system — callers say what they need instead of pressing numbers, and Mihu routes them into the extensions you already have.
Ways to deploy it
Because it's just an extension, you can start small and expand. Common patterns:
AI receptionist
Mihu answers the main line first, understands the caller, and routes them into the right extension — replacing the old menu.
Overflow
When every agent is busy, calls roll to Mihu instead of ringing out — so no one waits on hold or hangs up.
After-hours
Outside office hours, Mihu picks up — handling what it can and capturing the rest, instead of voicemail.
A dedicated line
Give Mihu its own number or queue for a specific job — bookings, a campaign, a department — and leave the rest untouched.
Setting it up
Adding Mihu to your PBX is the same kind of task as adding any new extension: create the extension, hand Mihu the SIP credentials, and route the calls you want it to answer. There's no migration and no downtime — your existing extensions keep working exactly as before while Mihu comes online alongside them.
If you'd rather have the bigger picture of bringing Mihu into a phone environment, the PBX & IVR integration guide covers it end to end, and you can shape how the agent behaves and when it escalates with guard rules and escalation.
Why it matters
- Keep your investment. Your PBX, numbers, and extensions stay exactly as they are — nothing to replace, nothing to port.
- Low-risk and incremental. Start with one number, one queue, or after-hours only, then expand as you see it work.
- Fast to deploy. Adding an extension takes minutes, not the months a system migration would.
- AI and humans on one system. Because Mihu lives inside your PBX, calls move between AI and people seamlessly — no awkward bridge between two separate worlds.
Addition, not replacement
You don't have to choose between the phone system you trust and the AI you want. Mihu slots into the one you already run — as an extension that answers, helps, and routes — so adopting AI is a small step, not a leap.
Frequently asked questions
Can Mihu work with my existing PBX?
Yes. Mihu registers into your existing PBX as just another extension over SIP, so you don't have to replace your phone system. It answers the calls you route to it and can transfer callers back to human extensions, departments, or external numbers.
Do I have to replace my phone system to use AI?
No. That's the whole point of running Mihu as an extension. Your PBX, numbers, and existing extensions stay exactly as they are — Mihu sits alongside them as one more extension that happens to be answered by AI.
Can Mihu transfer calls to a human?
Yes. After handling a call, Mihu can transfer or route it to a specific extension, a department or ring group, or an external number — handing the caller to the right person, with context where supported.
Which PBX systems does it support?
Mihu connects over standard SIP, so it works with common SIP-based PBX systems. The SIP Connector Setup guide covers the technical details of registering Mihu as an extension and pointing calls to it.
How do I set Mihu up as an extension?
You add Mihu to your PBX the way you'd add any softphone extension: create the extension, give Mihu the SIP credentials, and route the calls you want it to answer. The full walkthrough is in the SIP Connector Setup guide.
Add AI without touching your phone system
Bring Mihu online as an extension on the PBX you already run — answering, helping, and routing your callers from day one.
Add Mihu to your PBX Registers over SIP · No migration · Routes back to your extensions