Epson LQ-300+ User Manual page 32

Note:
If there is a ground wire at the end of the cable, attach it to the ground
connector located to the right of the serial interface port.
3. Plug the other end of the cable into the computer's serial
interface port and then tighten the screws on both sides of the
connector. (If there is a ground wire at the end of the cable,
attach it to the ground connector at the back of the computer.)
4. Use the Default Setting mode to change the baud rate or parity
bit, if necessary. See "About Your Printer's Default Settings"
on page 2-3.
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Setting Up the Printer