Star Micronics LC-8021 User Manual page 20

14 Printer Setup
Attach one end of the serial cable to a serial port of your computer (COM1,
COM2), and secure the connector with the screws provided on the plug.
Plug the other end of the cable into the socket on the back of the printer and
secure it in place with the screws.
Note:
The parallel interface equipped on the printer as standard can be removed and
replaced with an optional IS-NP192 Serial Interface Unit. This makes it
possible to connect two separate computers for serial data communication.