Test box for earth leakage current measurement.
Some details:
• Red CEE plug (probably 16A or 32A, 400V) – indicates that it is intended for a three-phase industrial environment.
• The text “Measure earth leakage current” indicates that the box is used to check for current that unintentionally flows through protective earth.
• Red push button – likely to activate the measurement or cut off the power.
• Lamp labeled “WARNING Protective earth broken” – indicates that the protective earth is temporarily disconnected to measure any leakage current, which must be done with caution.