What is ISDN connection?

ISDN is an acronym for Integrated Services Data Network. ISDN is a set of communication standards for transmitting data, voice, video or any other network services simultaneously over the traditional circuits of the PSTN (Public Switched Telephone Network). Actually, ISDN is a circuit-switched telephone network system that allows you to use the same pair of wires for multiple services. ISDN generally has two configurations, namely BRI (Basic Rate Interface) and PRI (Primary Rate Interface). The main difference is between the two types of connections is that BRI provides two 64kbps links while PRI provides either 30 64kbps lines or 24 64kbps lines – depending on E1 or T1 connectivity.

What is needed?

In order to create a reliable ISDN connection, your need the followings:

• a PC on which an IP PBX has been installed
• an ISDN phone line subscription
• a CAPI compatible ISDN card or USB device

Prerequisites in more details + How can I get them?

• Due to the enormous technological improvement of the last few decades, IP-based telephone systems have become more and more popular among the enterprises. This way, if you want to initiate phone calls through ISDN, you need to install a reliable IP PBX that ensures stable operation. Several phone systems can be found in the IT market, but it is worse to compare them and take into consideration their advantages, disadvantages and system requirements before buying. But what should you know foremost? Let's see the example of Ozeki Phone System XE. If you want to install it, firstly be sure that at least Window XP has been installed on your PC. In addition, you need .NET Framework 4.0. Moreover, make sure that you have enough RAM, appropriate CPU and HDD with sufficient free space. Obviously, all of the huge IP PBX developers have an own website (such as http://ozekiphone.com/how-to-use-pstn-devices-451.html ), where every necessary information are available. Almost each PBX can be downloaded from their websites, and a free trial version is usually available.
• Next to the corporate phone system, an ISDN phone subscription is essentially needed. For this purpose, do not hesitate to contact your mobile service providers (such as AT&T, T-Mobile, Vodafone, etc.), since they are willing to help you in designing the most appropriate, customized offer for you. As their price plans can be really varied, take your time to compare their offers.
• Last but not least, you need to attach a CAPI compliant ISDN card or USB device to your PBX. You can choose from numerous devices, as many manufacturers (AVM GmbH, Eicon Networks GmbH, Gerdes Aktiengesellschaft, ComIDSN, etc.) offer different kind of CAPI products. Useful tip: before purchasing, be sure that the particular CAPI device is compatible with your PBX. Using the previous example, Ozeki Phone System XE can be perfectly used with AVM Fritz! Box – next to many other devices.

Information source: http://ozekiphone.com/how-to-connect-to-isdn-lines-451.html