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Does a device with an external communication port of some kind fall under "intentional radiation" or "unintentional radiation" according to the FCC for testing and certification requirements?

For the purpose of this question, the external connection would be outside of the device's enclosure and must be connected via wire to communicate; it does not use the air as a communications medium. For example:

Lower frequency ports:

  • CAN Bus (which is the reason I'm writing)
  • RS232
  • I2C
  • SPI

Higher frequency ports (Are there others of note for the purpose of this discussion?):

  • USB
  • Ethernet
  • MoCA (multimedia over coax)

Are there some above that would be considered intentional and others that are unintentional radiation?

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3 Answers 3

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An unintentional radiator (defined in Section 15.3 (z)) is a device that by design uses digital logic, or electrical signals operating at radio frequencies for use within the product, or sends radio frequency signals by conduction to associated equipment via connecting wiring, but is not intended to emit RF energy wirelessly by radiation or induction.

Today the majority of electronic-electrical products use digital logic, operating between 9 kHz to 3000 GHz and are regulated under 47 CFR Part 15 Subpart B.

Examples include: coffee pots, wrist watches, cash registers, personal computers, printers, telephones, garage door receivers, wireless temperature probe receiver, RF universal remote control and thousands of other types of common electronic-electrical equipment that rely on digital technology. This also includes many traditional products that were once classified as incidental radiators – like motors and basic electrical power tools that now use digital logic.

From https://www.fcc.gov/oet/ea/rfdevice

So all of these fall under sends rf signals via connecting wiring

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  • \$\begingroup\$ The last coffeepot I in inspected in detail used an LM8560 clock chip which operates at 50 or 60Hz \$\endgroup\$ Jul 25, 2020 at 5:32
  • \$\begingroup\$ @Jasen Incidental Radiators: Examples of products that are classified as incidental radiators include: AC and DC motors, mechanical light switches, basic electrical power tools (that do not contain digital logic). and Unintentional Radiators: This also includes many traditional products that were once classified as incidental radiators – like motors and basic electrical power tools that now use digital logic. Yeah, some coffee pots are still old school analog circuits with a clock chip, while some are mHz micro controllers or IOT SOCs. The example list is not absolute. \$\endgroup\$
    – Passerby
    Jul 25, 2020 at 5:57
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Intentional radiation means rf radiation, i.e., a wireless transmitter.

None of the examples you mentioned are intentional radiators.

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The answer is "Yes." None of your examples constitute intentional radiation. Pretty much all modern digital devices would be classified by the FCC as unintentional radiators unless they have a transmitter. If they have a transmitter, then they are intentional radiators. They still need to satisfy all requirements of unintentional radiators except in the band where the transmitter is authorized to operate. In that band, the intentional radiator band, they would be required to meet band-specific FCC regulations. You may wish to enter the following into your favorite search engine: "title 47 part 15".

In many cases, compliance testing can be greatly simplified if you use a pre-certified module for things like bluetooth and wifi and gsm (or other mobile).

Outside the USA, different rules apply, but they are somewhat similar in regards to intentional and unintentional radiators.

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