Asterisk is a huge plus is that it is OpenSource-project. Ie Asterisk is not just free - it can be modified under any needs. Through an open license, Asterisk actively developed and supported by thousands of people from all over the world.

Generally speaking, IP PBX based on Asterisk can completely replace the usual MiniATS. To do this you need two types of ports: external (FXO) and internal (FXS). These ports can be found in the server specific PCI-card, which usually have several RJ-11. The fact that the main sponsor of the project is owned by Digium, which just makes such payment telephony, as well as other devices, and successfully sells them worldwide Solutions for ISP's.

Presence on the board FXO port allows you to connect to the city analog telephone line. In turn, the FXS ports are designed for simple connection of analog phones or faxes to the server. But if all subscriber devices are SIP-phones, the FXS card is no longer needed.