継電器

1. Origins, structure, and basic meaning

• Structure: 継電器 is read as けいでんき and is a technical noun for an electrical relay that switches circuit contacts in response to a signal.
• Basic usage: The component being replaced takes を in 継電器を交換する, while the operating component takes が in 継電器が作動する.

2. Common pitfalls and similar expressions

• Relation to リレー
  • リレー is the common loanword for the same electrical component; 継電器 is the Sino-Japanese technical term.
• Subject and object
  • The relay takes を when it is replaced and が when its own operation is described.