2N Helios IP Verso Installation Manual page 260

Cleaning
If used frequenly, the device surface, the keypad in particular, gets dirty. To clean it,
use a piece of soft cloth moistened with clean water. We recommend you to follow
these principles while cleaning:
Never use aggressive detergents (such as abrasives or strong disinfectants).
Use suitable cleaning agents for glass lens cleaning (cleaners for glasses, optic
devices screens, etc.)
Clean the device in dry weather in order to make waste water evaporate quickly.
Warning
Prevent water from getting inside the intercom.
Do not use alcohol-based cleaners.
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