Scantron OpScan 4ES Operator's Manual page 46

Chapter 2: Setting Up Your Scanner
Connecting the Scanner
26
3.
Plug the rectangular end (three receptacles) of the
power cable into the open end (with three prongs)
of the power supply.
4.
Plug the rounded end of the power supply into the
power port on the back of the scanner.
CAUTION: Do not plug the rounded end of the
power
supply into any part of the computer.
Scantron OpScan 4ES and NSIGHT 4ES Scanners