DC Power Plug and Jack

https://www.denshi-trade.co.jp/documents/dcplug/DCjack.htm

https://faq.as-1.co.jp/faq/show/168555

https://eleshop.jp/shop/pages/acadp_select.aspx

https://www.kamidenshi.co.jp/products/1767

NEC Aterm routers uses EIAJ-04 DC power plug

Most standard power adapter plug uses 5.5 x 2.1 mm