Terminology and abbreviations

PE and the earthing symbol
Terminology and abbreviations 1:

PE is the abbreviation for "protective earth" and has the same meaning as the earthing symbol
Terminology and abbreviations 2:

Earth, ground

The terms earth and ground are synonymous and are used interchangeably in this document.

T.b.d.

Still to be defined, value or description will follow in due course.

AC 400 V

A value preceded by "AC" or "DC" represents a nominal voltage or a nominal voltage range. The nominal voltage or the nominal voltage range may be provided with tolerances. (e.g., AC 380 - 480 V ±15%). The calculated total range then indicates the working range of the device.

Example:
DC 12 V refers to a 12 V battery, regardless of whether it is fully charged (13.7 Vdc) or discharged (10 Vdc).

400 Vac

A value followed by the unit Vac or Vdc is an instantaneous value that does not contain any additional tolerances.

50 Hz vs. 60 Hz

Unless otherwise specified, AC 230 V parameters are valid at a mains frequency of 50 Hz.

may

A keyword indicating a choice without implied preference.

shall

A keyword indicating a mandatory requirement.

should

A keyword indicating a choice with a clearly preferred method of implementation.