page_title: Tetrapolar plug
hierarchical_section_title: Tetrapolar plug
caption_attribution_description: English: Belgian tetrapolar telephone plug
context_page_description: A standard tetrapolar telephone plug has four round metal pins and one plastic pin. The design is only used in Belgium for telephone wiring. It is similar to the tripolar telephone plug of Italy and also the Swedish telephone plug.
  The plastic pin adds a presence function. When not inserted into a jack, the jack itself connects the incoming line to the next socket. The article on the Swedish telephone plug details its functional principles.
context_section_description: A standard tetrapolar telephone plug has four round metal pins and one plastic pin. The design is only used in Belgium for telephone wiring. It is similar to the tripolar telephone plug of Italy and also the Swedish telephone plug.
  The plastic pin adds a presence function. When not inserted into a jack, the jack itself (mechanically) connects the incoming line to the next socket. The article on the Swedish telephone plug details its functional principles.
caption: Belgian tetrapolar telephone plug. Note the four metal pins and the single plastic pin.
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