Epson TM-U200D series Operator's Manual page 21

2. Plug the power supply's cable into the printer's connector as
shown below. Note that the flat side of the connector faces
down.
Model with serial
interface
Model with
parallel interface
3. Plug the power supply's cord into an outlet.
If you ever need to remove the cable, unplug the power
supply's cord from an outlet and then grasp the connector
firmly at the arrow mark and pull it straight out.
1–10 Setting Up the Printer