Brother QL-570 - Manual (Page 18)

STEP1 Getting started 12
Important
For USB interface, the included USB interface cable should be used to
ensure compliance with the limits for EMC (Electromagnetic
compatibility).
For serial and network interfaces, a shielded interface cable should be
used to ensure compliance with the limits for EMC.
Changes or modifications not expressly approved by Brother Industries,
Ltd. may affect the performance and print quality, and damage may not
be covered under the limited warranty.
• Caution for LAN connection
Connect this product to a LAN connection that is not subjected to overvoltages.
• Caution for RS-232C connection
The RS-232C serial connector part of this equipment is not Limited Power Source.