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.
“Cloud PBX” is practically the same as the telephone system, only it
works within the Internet means, not the simple telephone line. Using this
service you don’t have to worry about how flexible and reliable is your
telephone system anymore.