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.
Call
Origination is the collecting of the call started by a calling party on a PSTN,
and handing off the call to a VoIP endpoint or to other exchange phone company
for completion to a called party
Call
Termination is a handing off or routing of calls from one Telephone Company to
another.