The FCC marking
All commercial electronic devices sold in the United States are regulated by the Federal Communications Commission (FCC) if they employ clocks or oscillators, operate at a frequency of greater than 9 kHz, and use digital techniques. This includes almost every product that contains a microprocessor.
Class A Device: devices marketed for use in an industrial or business environment and not intended for use in the home or a residential area.
Class B Device: devices marketed for use in the home or a residential area. Examples of such devices include, but are not limited to, personal computers, calculators, printers, modems, many electronic games, and similar devices that are marketed to the general public.