tocsin / toxin are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
tocsin: (noun) the sound of an alarm (usually a bell). (noun) a bell used to sound an alarm.
toxin: (noun) a poisonous substance produced during the metabolism and growth of certain microorganisms and some higher plant and animal species.
tocsin: NA
toxin: t·AA·k·s·ah·n
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)