Are you going to replace your video intercom and don’t know whether you have a 2-wire or 4+N-wire system? It’s the most common question we get. In this guide, we explain it clearly so you don’t make mistakes when buying.
Main differences: 2-wire vs. 4+N at a glance
| Feature | 2-wire BUS SCS system | 4+N-wire system |
|---|---|---|
| Number of wires | 2 wires at the terminal | 4 or more wires at the terminal |
| Installation period | From the 2000s onward | Before 2000 (mainly) |
| Technology type | Digital BUS | Conventional / analog |
| Polarity | No polarity | Each wire has a specific function |
| WiFi compatibility | Yes (monitors with mobile app) | No (without upgrading the wiring) |
| Monitor expansion | Easy, with no additional wiring | Requires more wiring |
| Are they compatible with each other? | No. They are incompatible systems. | |
What is a 2-wire system (BUS SCS)?
The 2-wire BUS SCS system is Tegui/BTicino’s most modern technology. As its name indicates, it uses only 2 wires to transmit audio, video, and power. It is the system installed in most homes built or renovated from the 2000s onward.
Advantages of the 2-wire system
- Simpler and more affordable installation
- Only 2 wires between the entrance panel and monitor
- No polarity: the connection order does not matter
- Compatible with modern monitors with WiFi and app
- Easy expansion to multiple monitors
✅ Tegui Series 8 monitor (Ref. 374494) — For 2-wire systems →
✅ Classe 100X16E WiFi monitor (Ref. 344786) — 2 wires with mobile app →
What is a 4+N-wire system?
The 4+N-wire system is the older conventional or analog technology. It uses 4 or more wires, each with a specific function (audio, video, power, door release, etc.). It is the typical system in homes built before 2000.
4+N-wire system features
- More wires and specific connections
- Each wire has a specific function
- Compatible with universal intercom handsets such as the Tegui T-71U (ref. 374240)
- Fewer modernization options without replacing the wiring
✅ Tegui T-71U intercom handset (Ref. 374240) — For 4+N systems →
How can I tell which one I have?
It’s very simple: remove the monitor or intercom handset from the wall and count the wires connected to the terminal:
- ✅ 2 wires → you have a 2-wire BUS SCS system (modern Tegui/BTicino)
- ❌ 4 or more wires → you have a 4+N-wire system (conventional analog)
Another clue: if your entrance panel has a sticker or engraving that says «BUS» or «SCS», it is a 2-wire system.
⚠️ Attention: do not count the wires in the conduit or wall, only those connected to the monitor terminals. Older installations may have unused wires that make counting difficult.
Are they compatible with each other?
No. 2-wire and 4+N systems are not compatible. A monitor designed for 2 wires will not work in a 4+N installation, and vice versa. That is why it is essential to identify your system before purchasing any component.
If you have a 4+N system and want access to modern features (WiFi, mobile app, color video), you would need to change the wiring to 2 wires. In many cases, it is quicker than it seems, especially in single-family homes.
Quick summary: what to buy for your system
| Your system | Recommended product | Reference |
|---|---|---|
| 2 wires at the terminal (BUS SCS) | Tegui Series 8 monitor | 374494 |
| 2 wires + I want WiFi | Classe 100X16E WiFi monitor | 344786 |
| 4+ wires at the terminal (4+N) | Tegui T-71U handset | 374240 |
⚠️ Do you still have questions? Send us a photo of your installation and we will tell you exactly which system you have and which product you need.
Frequently asked questions
Can I install a 2-wire monitor in my 4+N installation?
No. 2-wire BUS SCS and 4+N systems are electrically incompatible. Connecting a 2-wire monitor to a 4+N installation will not work and may damage the equipment.
How do I know how many wires my video door entry system has without taking it apart?
If you can access the entrance panel, look for a label or engraving: if it says «BUS» or «SCS», it is a 2-wire system. If you cannot see it without disassembling anything, the most reliable method is to remove the monitor from the wall and count the wires connected to its terminals.
Is the 2-wire system better than 4+N?
For new installations, yes: the 2-wire system is easier to install, allows easy expansions, and is compatible with modern WiFi monitors. The 4+N system is still perfectly suitable for replacing components in existing installations.
Can I upgrade my 4+N installation to 2 wires?
Yes, although it requires changing the wiring between the entrance panel and the monitors. In single-family homes, this is usually a minor job. In apartment blocks, it depends on access to the shared installation.
What if I have 3 wires?
There may be an unused wire in a 2-wire installation, or it may be a hybrid installation. The safest option is to note the numbers or letters of the terminals where the wires are connected and contact us before purchasing.