#  Introduction

- [Introduction](https://www.roger.pl/en/products/racs-4-access-control-system/introduction)
- [Software](https://www.roger.pl/en/products/racs-4-access-control-system/software)
- [Integrations](https://www.roger.pl/en/products/racs-4-access-control-system/integrations)
- [Network Controllers](https://www.roger.pl/en/products/racs-4-access-control-system/network-controllers)
- [Access Controllers](https://www.roger.pl/en/products/racs-4-access-control-system/access-controllers)
- [Proximity Readers](https://www.roger.pl/en/products/racs-4-access-control-system/prt-proximity-readers)
- [Expanders](https://www.roger.pl/en/products/racs-4-access-control-system/expanders)
- [Communication Interfaces](https://www.roger.pl/en/products/racs-4-access-control-system/communication-interfaces)

**The RACS 4 is a networked access control system based on single door access controllers, readers, communication interfaces, expanders, network controllers, and managing software.**

System functionality depends on the type of equipment used in a particular installation. The RACS 4 can be divided into separate branches which are called access networks or subsystems. Up to 250 networks can be integrated into a single access control installation. Each network may have up to 32 access controllers connected to the RS485 communication bus and with a distance of up to 1200m. The PR Master software communicates with the individual network through a separate serial communication port (COM or USB) or through a computer network (WAN or LAN). The RACS 4 is dedicated to small or middle-size access installations and is capable to handle up to 1000 controllers and depending on the PR series up to 4000 users (PRxx2) or 1000 users (PRxx1).

![RACS4 Structure](https://www.roger.pl/images/kontrola-dostepu/system-kontroli-dostepu-racs-4/wprowadzenie/racs4-structure-en.png "RACS4 Structure")

![RACS 4 Access Control System](https://www.roger.pl/images/kontrola-dostepu/system-kontroli-dostepu-racs-4/wprowadzenie/racs4-structure-internal-en.png "RACS 4 Access Control System")