[′bel tranz‚fȯr·mər] (electricity) An iron-core, step-down transformer with a voltage step-down ratio of approximately 6 to 1 or 12 to 1, used in low-current power supplies and frequently in circuits for doorbells, alarm bells, and buzzers.
bell transformer
A small transformer which supplies power, at low voltage, for operating a doorbell or the like.