1.1 These requirements apply to transformers, autotransformers, and motor-transformers intended to be used in audio-, radio-, and television-type appliances in which the primary winding is connected across the supply circuit.

1.2 The requirements in Sections 6 – 17, 25 – 28, 30, and 31 also apply to transformers intended for use in high-frequency, switching-type power supplies in which the transformer provides isolation from the supply circuit.

1.3 These requirements do not apply to transformers that are intended to transform only audio, video, and other signal waveforms. Those transformers are covered by the Standard for Isolating Signal and Feedback Transformers for Use in Electronic Equipment, UL 1876.

1.4 These requirements apply to a transformer or motor transformer that includes a separate current-limiting impedance such as a positive temperature coefficient (PTC) device complying with the requirements for thermistor-type devices, or a resistor complying with the Standard for Fusing Resistors and Temperature-Limited Resistors for Radio- and Television-Type Appliances, UL 1412.