# 1 Installation of the PortSIP PBX

### PortSIP PBX Free Edition

You can install the **PortSIP PBX Free Edition**, which supports up to **3 simultaneous calls** and **10 registered extensions**.

If you require higher capacity—for example, more concurrent calls or additional extensions—please refer to the [PortSIP PBX Pricing](https://www.portsip.com/portsip-pricing/) page for detailed licensing options.

***

### Supported PortSIP PBX Versions

PortSIP PBX currently maintains two active major versions:

* **v22.x** – Actively developed and fully supported
* **v16.x** – In maintenance mode; no new features are being developed

> ❗**Recommendation**\
> For optimal performance, security, and access to the latest features, we strongly recommend installing the latest **v22.x** release.

If you are currently running **v16.x**, we strongly recommend upgrading to **v22.x** to ensure ongoing compatibility and to benefit from continued enhancements and fixes.

***

### PortSIP ONE App Compatibility

Starting with **PortSIP PBX v22.0**, PortSIP introduced the all-new [PortSIP ONE](https://www.portsip.com/portsip-one/) application.

PortSIP ONE provides a modern, unified business communications experience with a comprehensive set of features. However, please note the following compatibility requirements:

* PortSIP ONE is compatible only with PortSIP PBX v22.x
* PortSIP ONE is not compatible with PortSIP PBX v16.x
* The [legacy PortSIP softphone](https://www.portsip.com/portsip-softphone), which worked with **v16.x**, is not compatible with **v22.x**

> ❗**Important**\
> Ensure your PBX version and client applications are compatible before upgrading or deploying new client software.


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