警笛

1. Origins, structure, and basic meaning

• Structure: 警笛, read けいてき, denotes a warning horn or whistle sounded by a train or ship to attract attention.
• Basic usage: It names a train horn at a crossing and a short warning signal sounded by a ship in fog.

2. Common pitfalls and similar expressions

• An audible warning of danger
  • It is sounded by a vehicle or vessel to attract attention and warn of danger, not as music or an ordinary alert.