A Tannoy is a loudspeaker system used to make announcements in a public place — a train station, an airport, a school, a factory, a sports ground. Someone speaks into a microphone in an office somewhere, and the voice comes out of speakers on the ceiling so hundreds of people hear it at once. The important thing to know is that this is a brand name that swallowed the general word. Tannoy Ltd is a real British company that made these systems, and in Britain the name became the everyday word for any public address system, whoever made it — the same way people in Taiwan say 大聲公 or use a brand name for a product. This means it is strongly British: an American would say "the PA" or "the loudspeaker" and might not know Tannoy at all. It works as a verb too, and this is very common in British speech: "They tannoyed his name" means an announcement was made calling for him. British speakers usually write it with a small t when using it as an ordinary word, though the company spells it with a capital T. It carries a slightly institutional, everyday-British flavour — hospitals, stations, schools — and often a hint of a crackly, hard-to-hear voice.

公共廣播系統、擴音器（車站、學校、機場的廣播）。台灣說「廣播」「校園廣播」「站內廣播」；英國人常直接說 Tannoy，但這是英式用法，美國人多半說 PA (public address) system 或 loudspeaker。這種「品牌名變成通稱」的情形，就像台灣人講「舒潔」指衛生紙、「宅急便」指快遞一樣。