The XCP-16-DB9-T is the newly created 16-port DB9 breakout panel with MDR connector and an audio transformer for the Cronus and AIO-16. It allows you to expand the number of DB-9 serial ports in the intercom system. NOTE: When using the 32-port DB-9 breakout panel, you MUST use the MDR backcard for both the AIO-16 and Cronus.