Dascom TallyCom III 2440/2540 Quick Installation Guide - Manual (Page 4)

3 Take the interface module and make sure that the
two screw openings are pointing to the right. Slide
the interface module into the guides and push it
carefully into the printer until the connector of the
interface module is properly seated into the socket.
Fasten the interface module with the two screws to the
printer. The left example shows the RS232C interface,
the right example the Ethernet interface.
4 Connect the interface cable to the printer and the
computer.