The bell transformer TD-230V-/3-5-8V/0.5A reduces the voltage of the electrical installation from 230V to the level of 3, 5, 8.12V or up to 24V depending on the design. The rated power of bell transformers on the market is usually from 4 to 16VA.
They are mainly used to power the home electric bell, also for electromagnetic locks, to power alarm devices, etc., for security reasons.