Multiple socket outlets fall under the German safety standard DIN VDE 0620-2-1, which must be fulfilled.
In this standard, the structure (design) is differentiated into
reconnectable plugs and sockets (plug and coupling socket), which must be equipped with screw terminals, and
non-reconnectable, which must be equipped with permanently effective connections (e.g. soldered, welded or crimped connections) (screw terminals are not permitted).
The “non-reconnectable” type is accompanied by the normative requirement that it must not be possible to disconnect the flexible cable without rendering the connector permanently unusable. Furthermore, it must not be possible to open either plugs or coupling sockets by hand or with a hand tool. One-way screws are expressly suitable for this purpose.
The background to this normative requirement is that it must not be possible for end users to make changes to permanently effective connections (e.g. soldered, welded or crimped connections), because it cannot be assumed that everyone can do this technically correctly. This is intended to avoid a potential safety risk.
The manufacturer's choice of connector type may be due to the installation space or because one type offers advantages during the heating test.
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