The MAX 1800 is availablein two versions. There is a BRI U ( US) and a BRI S (Europe and other countries).

From the back, both look equal.

But internally here on this BRI U board version, the NT (network terminator) is onboard.

In Germany we have BRI S versions only. That means, you may connect up to eight ISDN terminals to one 4 wire line.

On a BRI U, the MAX 1800 port is the only unit on that 2 wire line.