Brother DCP-4020C - Manual (Page 201)

14 - 4 IMPORTANT INFORMATION
IMPORTANT-For Your Safety
To ensure safe operation the three-pin plug supplied must be
inserted only into a standard three-pin power point which is
effectively grounded through the normal household wiring.
Extension cords used with the equipment must be three-conductor
and be correctly wired to provide connection to ground. Use of
extension cords is not recommended.
The fact that the equipment operates satisfactorily does not imply
that the power is grounded and that the installation is completely
safe. For your safety, if in any doubt about the effective grounding of
the power, consult a qualified electrician.
IT Power System (For Norway Only)
This product is also designed for IT power distribution system with
phase-to-phase voltage 230V.