How to tune your FRITZ!Box into a professional call server

Anyone who works from home or runs a small business knows the problem: The standard features of the FRITZ!Box are great, but sometimes the integrated answering machine just isn’t enough. Do you want to record calls for documentation purposes? Do you need timed announcements that automatically play during lunch breaks?

The good news: You don’t need to buy an expensive phone system. A Windows laptop and your existing FRITZ!Box are all you need. In this article, I’ll show you how to transform your computer into a powerful call server.

Connecting a Fritz!Box to a laptop - telephone exchange

What is possible? 3 application examples

Before we delve into the technical details, here are three scenarios you can implement with this setup:

The intelligent “opening hours” monitor: A caller rings at 12:30 PM. Your system recognizes: It’s lunchtime. Instead of simply ringing, the laptop immediately answers the call and plays a professional message: “We’re currently having lunch, but will be back at 1:00 PM.” At 1:01 PM, the system automatically switches back to “call forwarding.” A caller calls are being forwarded.

Legally Compliant Order Acceptance: Do you take orders or complex briefings over the phone? With one click, you can record the call so you don’t forget any details later. (Note: See legal information below!)

The Automatic Receptionist: Are you focused on your work and don’t want to be disturbed? The laptop answers all calls, plays a message (“I’m in a meeting”), and records the message, which is then saved directly to your desktop as a file.

The Tools

For this tutorial, we’ll be using a combination of hardware and free software:

Hardware: An AVM FRITZ!Box (any model will do) and a Windows laptop/PC.
Software: Phoner (Important: Not “PhonerLite”, but the full version “Phoner”). The tool has a somewhat retro look, but it’s a Swiss Army knife for telephony.

Phoner Download page

Attention: Legal Notice (§ 201 StGB German Law)

Before we begin, a serious word: In Germany, recording “non-publicly spoken words” without the consent of all parties involved is a criminal offense.

Answering machine: This is not a problem, as the caller knows they are speaking to a recording.
Call recording: You must ask your conversation partner beforehand (“Is it okay if I record the conversation to confirm the order?”). Only after receiving a “Yes” may you press the record button.

Step-by-step instructions

Step 1: Cabling & Hardware Requirements

Many users think they need to plug a standard telephone cable from the FON 1 port of the FRITZ!Box into their laptop. That’s incorrect! Since we’re using VoIP (Voice over IP), calls are routed digitally over your home network.

Which cables do you need?

You only need a network connection between your laptop and the FRITZ!Box.

Recommendation (LAN cable): It’s best to connect your laptop to the FRITZ!Box using a standard Ethernet cable (LAN). This guarantees a smooth, uninterrupted connection.
Alternative (Wi-Fi): It also works wirelessly via Wi-Fi. Make sure your laptop has a good Wi-Fi signal. A weak signal can lead to choppy audio or delays.

If you can browse the internet on your laptop, it’s also ready for phone calls. A special audio or phone cable isn’t necessary.

Operating System: For the recommended software Phoner, you need Windows (Windows 10 or 11 are ideal, older versions often work as well). Mac or Linux users will have to resort to alternatives such as Linphone or Zoiper, although the setup process differs slightly.
Audio Hardware (Headset vs. Speakers):
- For Answering Machine Use Only: If the laptop is only intended to play and record announcements, the internal sound card is sufficient. You don’t need to connect external speakers. You will need a microphone (or the laptop’s built-in microphone) briefly to record the announcements.
- For Making Phone Calls: If you also want to make calls using the laptop, a USB headset is essential. The built-in microphones and speakers of laptops often produce an unbearable echo (feedback) for the caller.
IMPORTANT: The power settings! This is the most common source of problems. A laptop that is “asleep” cannot make phone calls.

You must disable standby (hibernation) mode in the Windows power options when the device is plugged into the power adapter.

The screen may turn off, but the computer must continue running in the background (never enter hibernation).

Step 2: Prepare the FRITZ!Box

We need to tell the FRITZ!Box that the laptop is a telephone.

Open fritz.box in your browser and log in.
Go to Telephony > Telephony Devices in the menu.
Click on Set up new device on the right.
Select Telephone (with and without answering machine) and click on “Next”.
Select LAN/WLAN (IP phone) and give the child a name (e.g. “Laptop server”).
Important: Now set a username and password. (Write it down, we’ll need it in a moment).
In the next step, select the phone number that the laptop should respond to (e.g., your office number).
Complete the setup.

Step 3: Setting up Phoner on the laptop (Windows)

Download and install Phoner (Full Version).
The settings menu opens on first launch (or under Options > Communication).
Select the SIP tab.
Now enter the data from the FRITZ!Box:
- Proxy/Registrar: fritz.box (or 192.168.178.1)
- STUN Server: Leave blank.
- Username: The name from step 1 (e.g., “Laptop Server”).
- Authentication Name: Often the same as the username; otherwise, try leaving it blank.
- Password: The password from step 1.
Click OK. A green dot or “registered” should now appear on the left side of the bar at the bottom. If your landline rings, your laptop will ring too!

Step 4: Configure the Call Server (Answering Machine & Time Control)

Now comes the magic. In Phoner, there’s an Answering Machine tab (often found as an icon or in the menu).

A. Create Announcements: Record your announcements using the Windows Audio Recorder or directly in Phoner and save them as .wav files (e.g., midday.wav, end-of-work.wav, recording.wav).

B. Create Profiles: In Phoner’s options, you can create different profiles for the answering machine.

Create a “Lunch Break” profile.
Load the file (e.g., midday.wav) as the greeting text.
Set: “Answer after x seconds” (e.g., 0 seconds for immediate answering).
Check the “Record” box if the caller is allowed to speak.

C. Time Control (Phoner): Phoner allows you to set conditions. In the menu under Options > Answering Machine, you can specify when each profile is active. This requires some familiarization with Phoner’s scripting logic, but to begin with, it’s often sufficient to manually activate the answering machine with a single click when you go on break.

Step 5: Recording Calls

If you are on a call yourself (using a headset on your laptop) and want to record it:

Call the customer (or answer the call).
Ask for permission.

In the active Phoner call window, click the record button (red circle). The file will be automatically saved in the Phoner folder with a timestamp.

Conclusion

With relatively little effort, your laptop becomes the central hub. This solution is ideal for anyone who needs professional telephony features but is (still) hesitant about the cost and complexity of a cloud-based phone system.

The only drawback: Your laptop needs to be running for it to work.

Good luck with the setup! :)

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