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.
Notification about the incoming calls, addressed to your land line or
office phone, coming to your cell phone. For instance, if you had a call to the
office at the moment when you were unavailable, a notification about the missed
call will come to your mobile phone.