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.
Voice over IP gateway VG200 was specially created for Cisco AVVID (Architecture for Voice, Video and Integrated Data) Call Manager. This device was not meant to support add-ons, such as toll bypass using H.323 protocol or SIP gateways.