FCC Part 15 (47 CFR Part 15) is the US regulation covering radio-frequency devices that do not require an individual operating license. It sets legally binding emission limits for two broad device categories - unintentional radiators (Subpart B: computers, power supplies, digital electronics) and intentional radiators (Subpart C: Wi-Fi, Bluetooth, remote controls) - and defines the equipment authorization procedures a product must complete before it can be marketed in the United States. Measurements are performed per ANSI C63.4 or C63.10.

What does FCC Part 15 cover?

Part 15 covers any device that can emit radio-frequency energy, whether by design or as a by-product of digital operation. Its central legal principle, stated in Section 15.5, is that operation is permitted on two conditions: the device may not cause harmful interference, and it must accept any interference it receives. The rules then divide devices by intent:

• Unintentional radiators (Subpart B) generate RF energy internally but do not deliberately transmit it - computers, monitors, switching power supplies, LED drivers, most digital electronics. They must meet the conducted limits of Section 15.107 and the radiated limits of Section 15.109.
• Intentional radiators (Subpart C) deliberately transmit RF - Wi-Fi routers, Bluetooth devices, garage door openers. Each technology has its own technical rules (frequency bands, power limits) in Sections 15.201 through 15.257.

Incidental radiators (motors, mechanical switches) that generate RF only incidentally fall under general good-engineering obligations rather than numeric limits.

What are the FCC Class A and Class B radiated emission limits?

Class A equipment is marketed for use in commercial, industrial or business environments; Class B is marketed for residential use and must meet tighter limits. Section 15.109 publishes the radiated field-strength limits below (quasi-peak detector below 1 GHz; Class A is specified at 10 m, Class B at 3 m):

Above 1 GHz, average and peak detector limits apply per Section 15.109 and Section 15.35. Because field strength falls with distance, a Class B limit at 3 m is substantially stricter than a numerically similar Class A limit at 10 m. Section 15.109(g) has historically also permitted use of CISPR-based limits as an alternative; check the current rule text and FCC KDB guidance for what is accepted today.

Conducted emissions: Section 15.107 limits the RF voltage a device couples back onto the AC mains between 150 kHz and 30 MHz, measured with a 50 ohm / 50 uH LISN. Class B quasi-peak limits run from 66 dBuV (decreasing to 56 dBuV across 150-500 kHz) to 60 dBuV at 5-30 MHz, with average limits 10 dB lower; Class A limits are more relaxed (79/73 dBuV quasi-peak). See what is a LISN for how this measurement works.

How does FCC equipment authorization work (SDoC vs certification)?

Two authorization routes exist since the FCC consolidated its procedures in 2017:

• Supplier’s Declaration of Conformity (SDoC) - the manufacturer or importer tests the product (any competent lab), keeps the test report on file, and declares compliance. No FCC ID is issued. SDoC is available for unintentional radiators such as ordinary digital devices.
• Certification - required for most intentional radiators. Testing must be done at an FCC-recognized accredited laboratory, the application is reviewed by a Telecommunication Certification Body (TCB), and the device receives an FCC ID that must appear on the label and in the FCC equipment authorization database.

A product containing a radio module plus digital circuitry commonly uses both: certification for the transmitter, SDoC for the unintentional-radiator part.

What role does ANSI C63.4 play in FCC testing?

The FCC writes limits, not measurement procedures. Section 15.31 designates ANSI C63.4 as the measurement method for unintentional radiators, which means the test setup - table height, cable arrangement, turntable rotation, antenna height scan from 1 m to 4 m, site validation - all come from C63.4 rather than from the CFR. Donald N. Heirman chaired the working group that maintained ANSI C63.4 for many years; the standard is described on our ANSI C63 page and his career in the biography.

How does Part 15 compare with European requirements?

The biggest structural difference is immunity: Part 15 covers emissions only, while the EU EMC Directive requires immunity as well, typically via CISPR 35 or the IEC 61000-6 generics described on the IEC 61000 page. Emission limits are broadly similar in stringency to CISPR Class A/B limits but differ in measurement distances and detector details. For help deciding which class applies to your product and the labeling that follows, see FCC Class A vs Class B.