Lenovo ThinkPad X1 Carbon Type 20A7 20A8 - Manual (Page 17)

earphones you use also comply with EN 50332-2 (Clause 7 Limits) for a wide band
characteristic voltage of 75 mV. Using headphones that do not comply with EN
50332-2 can be dangerous due to excessive sound pressure levels.
If your Lenovo computer came with headphones or earphones in the package,
as a set, the combination of the headphones or earphones and the computer
already complies with the specifications of EN 50332-1. If different headphones
or earphones are used, ensure that they comply with EN 50332-1 (Clause 6.5
Limitation Values). Using headphones that do not comply with EN 50332-1 can be
dangerous due to excessive sound pressure levels.
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