47 CFR Parts: FCC rules by technology

Author Hugues Orgitello Last updated 25 May 2026

FCC · Pillar

FCC rules are organised into Parts of 47 CFR. Unlike the European approach based on harmonised EN standards, the FCC publishes technical requirements directly in the regulation. This page presents the most used Parts for IoT products, their main limits, and associated KDB publications that clarify their application.

47 CFR architecture

Title 47 of the Code of Federal Regulations covers telecommunications. Parts of interest for electronic products:

Part	Subject	Typical regime
2	Definitions, authorisation procedures	All
15	Unlicensed radio-emitting equipment + digital equipment	Certification or SDoC
18	ISM equipment (Industrial, Scientific, Medical)	Verification (legacy)
22	Public Mobile Services (historical cellular)	Certification
24	Personal Communications Services (PCS 1900 MHz)	Certification
27	Miscellaneous Wireless Communications (modern cellular, 5G)	Certification
74	Auxiliary Broadcast (professional wireless microphones)	Certification
80	Maritime Stations	Certification
90	Private Land Mobile (professional PMR)	Certification
95	Personal Radio Services (CB, GMRS, FRS)	Certification
96	Citizens Broadband Radio Service (CBRS 3.5 GHz)	Certification
97	Amateur radio	No commercial certification

For most modern IoT products, Part 15 is the principal Part, optionally complemented by Parts 22/24/27 for cellular modules.

Part 15: Unlicensed equipment

The most used Part. Subparts:

Subpart	Coverage
A	General definitions
B	Unintentional emitters (digital equipment)
C	Intentional emitters (unlicensed radio)
D	Ultra-wideband equipment (UWB)
E	U-NII (Wi-Fi 5/6 GHz)
F	Ultra Wide Band (detailed subpart F)
H	Very high frequency equipment (60 GHz)

Part 15 Subpart B: Digital equipment

Covers all digital equipment (computers, microcontrollers, digital electronic equipment). Two classes:

• Class A: equipment intended for commercial/industrial environment (less strict limits, mandatory user warning).
• Class B: equipment intended for residential environment (stricter limits).

Class B conducted emission limits (Section 15.107):

Frequency	Quasi-peak	Average
150-500 kHz	66 to 56 dB(µV)	56 to 46 dB(µV)
500 kHz - 5 MHz	56 dB(µV)	46 dB(µV)
5 - 30 MHz	60 dB(µV)	50 dB(µV)

Class B radiated emission limits (Section 15.109):

Frequency	Limit at 3 m
30 - 88 MHz	100 µV/m (40 dBµV/m)
88 - 216 MHz	150 µV/m (43.5 dBµV/m)
216 - 960 MHz	200 µV/m (46 dBµV/m)
> 960 MHz	500 µV/m (54 dBµV/m)

Part 15.247: Spread spectrum 902-928 MHz and 2.4 GHz

The reference subpart for Wi-Fi 2.4 GHz and BLE. Main limits:

Parameter	Limit
Maximum output power	1 W (30 dBm)
Maximum antenna gain	6 dBi without reduction
Maximum EIRP	Depends on antenna gain
Spectral density	8 dBm in 3 kHz
Out-of-band emissions	Per specific masks

Important: FCC authorises 1 W conducted power in 2.4 GHz, vs 100 mW EIRP in EU. A full-power US product exceeds European limits.

Part 15.407: U-NII 5/6 GHz

Covers Wi-Fi 5 GHz (U-NII-1 to U-NII-4) and 6 GHz (U-NII-5 to U-NII-8) bands.

U-NII band	Range	Max power	DFS required
U-NII-1	5150-5250 MHz	30 dBm	No
U-NII-2A	5250-5350 MHz	24 dBm	Yes
U-NII-2C	5470-5725 MHz	24 dBm	Yes
U-NII-3	5725-5850 MHz	36 dBm	No
U-NII-5	5925-6425 MHz	30 dBm (LPI), 36 dBm (Standard Power with AFC)	No
U-NII-6	6425-6525 MHz	30 dBm (LPI)	No
U-NII-7	6525-6875 MHz	30 dBm (LPI), 36 dBm (Standard Power with AFC)	No
U-NII-8	6875-7125 MHz	30 dBm (LPI)	No

The introduction of AFC (Automated Frequency Coordination) for U-NII-5/-7 Standard Power bands is recent (2023) and requires dynamic coordination with a central system, additional complexity for outdoor equipment.

Working on choosing the applicable Part 15 sub-part for a product for a real product? AESTECHNO can audit your design and certification plan. Get in touch →

Cellular Parts: 22, 24, 27

Part 22: Public Mobile Services

Historically the Part for 850 MHz US cellular bands:

• A-band: 824-849 MHz / 869-894 MHz (formerly AMPS, today LTE B5)
• Still in use for LTE Band 5 and 5G n5

Part 24: Personal Communications Services

PCS 1900 MHz bands:

• 1850-1910 MHz / 1930-1990 MHz (LTE B2, B25, 5G n2, n25)

Part 27: Miscellaneous Wireless

The most used Part for modern cellular:

Bands	Typical uses
700 MHz (B12, B13, B14, B17)	LTE, FirstNet
1700 MHz (B4, B66)	LTE AWS
2100 MHz (B25, B66)	LTE PCS, 5G n25/n66
2300 MHz (B30)	LTE
2500 MHz (B41)	LTE TDD, 5G n41
3700 MHz (n77, n78)	5G mid-band

For a multi-band US LTE cellular module, the FCC file typically cites several Parts in parallel (24 + 27 by supported bands).

Sub-GHz: Part 15.247 vs Part 15.249

In the US, the 902-928 MHz band (ISM) is the counterpart of the European 868 MHz band. Two subparts may apply:

Part 15.247: Spread spectrum

Power up to 1 W with spread spectrum or frequency hopping. Used by:

• US LoRa 915 MHz
• Sigfox 902 MHz
• RFID UHF gen2

Part 15.249: Periodic operation

Lower power (50 mV/m at 3 m typically), but no obligation for spreading. Used by:

• Remote controls
• Low-power periodic sensors
• Simple active RFID tags

The choice between 15.247 and 15.249 depends on desired power and modulation complexity.

§ § §

KDB publications

The FCC KDB (Knowledge Database) publishes interpretations of 47 CFR rules. Some essential KDBs:

KDB	Subject
KDB 996369	Modular Approval (radio modules)
KDB 484596	Modular Transmitters
KDB 558074	Wi-Fi 5/6 GHz U-NII
KDB 935210	DFS and radars
KDB 942474	Variable frequency spread spectrum
KDB 922573	Hopping systems vs digital modulation
KDB 414788	Section 15.247 and 15.249
KDB 358029	UWB bands
KDB 387120	Compliance demonstration
KDB 178919	SAR and hand-held devices

KDBs are not formal rules but they guide TCBs in their judgement. For a non-standard product, consulting applicable KDBs is essential before submitting to a TCB.

Mandatory markings and warnings

The user manual must include standardised FCC mentions:

For intentional emitters (Part 15.19)

This device complies with part 15 of the FCC Rules. Operation is
subject to the following two conditions: (1) This device may not
cause harmful interference, and (2) this device must accept any
interference received, including interference that may cause
undesired operation.

For digital equipment (Part 15.105)

NOTE: This equipment has been tested and found to comply with the
limits for a Class B digital device, pursuant to part 15 of the
FCC Rules. These limits are designed to provide reasonable
protection against harmful interference in a residential
installation. [...]

Warning against modifications

For all certified products, add:

WARNING: Changes or modifications to this unit not expressly
approved by the party responsible for compliance could void the
user's authority to operate the equipment.

Omitting any of these warnings is a common ground for certification rejection.

In summary

• Part 15 is the principal Part for most IoT products
• Part 15.247 covers Wi-Fi/BLE 2.4 GHz and sub-GHz ISM
• Part 15.407 covers Wi-Fi 5/6 GHz
• Parts 22, 24, 27 cover cellular bands
• KDB publications are essential for non-standard cases
• Mandatory manual notices must not be omitted

For practical implementation, see FCC procedure and Required tests.

Sources & references

1. 47 CFR Part 15, full text , FCC www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15
2. FCC KDB publications , FCC apps.fcc.gov/oetcf/kdb/