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 service provides the information regarding the incoming SMS, voice or email messages. At the moment when the message comes, the telephone plays a signal. The system also allows setting filters, thus, allowing you to choose, which messages to inform you about and which to ignore.