Dell PRECISION WCM Information Manual page 16

To completely switch off the equipment, the power supply cable must be removed from the
power supply socket, which should be located near the equipment and easily accessible.
A protection mark "B" confirms that the equipment is in compliance with the protection
usage requirements of standards PN-93/T-42107 and PN-EN55022:1996.
PN-EN55022:1996.
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