It is a device capturing and controling all the signals, which are being created by the whole system, especially the made and received phone call signals. The device is mostly used for connecting regular phone system with the Internet and backwards.
The program asking you to enter the extension number of the person or department you are trying to reach. When the caller enters an extension number, the system asks the name of the caller in order to inform the called party about an incoming call, presenting the caller.