This is the Adtran Rackmount ISDN Service Unit, part number 1200074L1
This rack mount device installs in the Adtran Smart 16 shelf. This unit allows
high-speed data transmission (up to 128 kbps) using a single ISDN line.
The ISU 2X64 Rackmount features dual RS-530/RS-232 DTE interfaces.
Synchronous data transfer rates from 2400 bps to 128 kbps and asynchronous
rates from 300 bps to 115.2 kbps are supported on a single DTE interface.
This looks to be new in box with manual and phone lines.