[Home](/)/[Resources](/resources)/FCC Part 15 Class A vs Class B FCCEMCUS compliance # FCC Part 15 Class A vs Class B: Which Applies to Your Product? Getting this classification wrong means commissioning an entirely new FCC authorization — not an amendment. Class A and Class B have different emission limits, different intended environments, and different legal consequences. Here is how to classify correctly the first time. Copy Link[Share on WhatsApp](https://wa.me/?text=https%3A%2F%2Fkrono-labs.com%2Fguides%2Ffcc-part-15-class-a-vs-b) [Check my US compliance requirements](/platform/new) Background ## Why the classification exists FCC Part 15 Subpart B covers unintentional radiators — devices that generate radio frequency energy as a byproduct of their operation rather than for intentional transmission. Every digital device with a clock above 9 kHz qualifies. The FCC divides these devices into two classes because the regulatory risk is different depending on where the device operates. Residential environments are more sensitive to RF interference than commercial or industrial ones. Homes contain televisions, radios, baby monitors, and Wi-Fi routers operating in close proximity to digital devices. There is no trained technical staff on hand to troubleshoot interference. Commercial and industrial facilities operate under more controlled conditions with professional management. Class B limits are 6 to 10 dB tighter than Class A limits depending on the frequency band. That difference is enough to require entirely different PCB design decisions — trace impedance control, filtering strategy, chassis grounding — not just different test margins. By the time you are at the certification stage, these decisions are already locked into your hardware. Which is why getting the classification right at the design stage, not after submission, is the only viable approach. Classification ## Class A vs Class B: the defining criteria ### Class A — commercial and industrial Digital devices marketed for use exclusively in commercial, industrial, or business environments. The key word is _exclusively_. Products sold to enterprises, sold through B2B channels only, and with clear labelling prohibiting residential use qualify for Class A. Examples include industrial PLCs, rack-mounted server equipment, commercial digital signage systems, and enterprise networking infrastructure. ### Class B — residential and general consumer Digital devices intended to be used in a residential environment or that may be used in such environments. The phrase “may be used” is the operative test. Laptops, tablets, smartphones, smart home devices, consumer IoT devices, wearables, USB accessories, and any product sold through retail or e-commerce must meet Class B. Work-from-home patterns have expanded what “may be used in a residential environment” means in practice. ### The emission limit difference At 30 MHz, conducted emissions: Class A limit is 60 dBμV quasi-peak vs Class B at 48 dBμV — a 12 dB tightening. Radiated emissions at 30–88 MHz: Class A is 39 dBμV/m at 10 m vs Class B at 29.5 dBμV/m — a 9.5 dB tightening. These margins require meaningfully different design approaches, not just better component choices. ### The authorization difference Class A devices may use Supplier's Declaration of Conformity (SDoC) — no FCC filing, no grantee code, no FCC ID required. Class B devices with intentional radio transmitters must use Certification through an FCC-recognized Telecommunication Certification Body (TCB) and must carry an FCC ID. Class B unintentional radiators without radio may still use SDoC, but must include a Class B compliance statement in the user manual and product labeling. Decision process ## How to classify your product correctly 01 ### Identify all digital subsystems List every component that generates or uses timing signals above 9 kHz. This includes microcontrollers, FPGAs, switching regulators, oscillators, and any digital communication interfaces. FCC Part 15 Subpart B applies to the complete assembled device, not individual components. 02 ### Define your actual distribution channel Where will this product be sold and used? If the answer includes Amazon, consumer retail, direct-to-consumer e-commerce, or any channel where a residential buyer could purchase it, the product must meet Class B. The intent of the marketing claim does not override the actual distribution channel. 03 ### Apply the residential use test Ask: Is there any realistic scenario in which this product ends up operating in a residential environment? Remote work, home offices, consumer purchase through corporate expense accounts — all create residential exposure. If the answer is yes, Class B applies. Do not use Class A labelling to satisfy this test without genuinely restricting the distribution channel. 04 ### Design to the correct limit from schematic review Once classified, engineering decisions about crystal placement, power plane splits, common-mode chokes, and conducted emission filtering should target the correct class's limits with at least 6 dB of margin. Pre-compliance scanning before the final board revision can confirm you are on track before spending money on formal testing. 05 ### Apply correct labelling Class A devices require a specific FCC notice in the user manual stating that the equipment has been tested and found to comply with Part 15, Class A limits, that it may cause harmful interference to radio communications in residential installations, and that the user may be required to take corrective measures. Class B devices require a shorter standard FCC notice stating Class B compliance and non-guarantee of non-interference in particular installations. Common errors ## Classification mistakes that trigger enforcement 01 Certifying as Class A while distributing on Amazon or other consumer platforms — FCC enforcement treats distribution channel as determinative, not product labelling 02 Adding a Class A label to a product originally designed and tested to Class B limits — the label does not change the applicable standard 03 Treating Class A certification as valid for a product variant that will be sold through different channels than the original 04 Failing to include the required Class B or Class A compliance statement in user documentation — this is a separate violation from EMC test non-compliance 05 Using a Class A SDoC authorization for a product that has an intentional radio transmitter — intentional radiators always require Certification regardless of Class A classification 06 Assuming the FCC classification decision can be changed by amending the existing authorization — it cannot; a new authorization is required ## Learn this properly, not just for one product In-depth courses and books that teach the process — not a one-off answer you'll need to look up again next time. [Start the course — $149](/courses/02-fcc-authorization-for-hardware-startups)[Free Compliance Roadmap](/platform/new) [Prefer to read? Get the book — $24.99](/books/02-fcc-authorization-for-hardware-startups) ## Frequently asked questions ### What is the difference between FCC Class A and Class B? Class A covers digital devices marketed exclusively for commercial, industrial, or business environments. Class B covers devices intended for residential use or that may be used there. Class B limits are 6–10 dB tighter than Class A depending on frequency, because residential environments have no trained technical personnel and are more densely packed with receivers. ### Can I certify a product to Class A if it will also be sold on Amazon? No. If a product is distributed through general consumer channels — including Amazon, Best Buy, or any storefront accessible to residential buyers — it must meet Class B limits. Class A is only appropriate for devices that are marketed, sold, and used exclusively in commercial or industrial settings with no reasonable expectation of residential deployment. ### What does it cost to switch from Class A to Class B certification? Changing from Class A to Class B certification requires a completely new FCC authorization — it cannot be done as an amendment. You must commission new test reports to the tighter Class B limits. If your product fails Class B testing, a board revision and second test campaign are required. Total cost including redesign can reach $20,000–$50,000 and add 12–24 weeks to your schedule. ### What is a digital device under FCC Part 15? An unintentional radiator that uses digital techniques and whose operation generates and uses timing signals or pulses at a rate in excess of 9,000 pulses (cycles) per second. This includes CPUs, switching power supplies, oscillators, digital interfaces, and their associated peripheral devices. Most modern electronics with any digital logic qualify. [ Map your product, free Every standard, document, and test that applies — free, no account required. Start mapping](/platform/new)[ Want an expert to handle your compliance for you? One consultant from Krono's compliance team takes your product from requirements to legal sale, with a fixed quote before any work starts. See compliance services](/services) Learn this properly In-depth course that teaches the full process, not just this one answer. [Start the course — $149](/courses/02-fcc-authorization-for-hardware-startups)[Prefer to read? Get the book — $24.99](/books/02-fcc-authorization-for-hardware-startups) Related guides * [FCC SDoC: Supplier's Declaration of ConformityFCC SDoC explained: which devices qualify, required content, responsible party obligations, record-keeping, and when Certificat…](/guides/fcc-sdoc-supplier-declaration) * [FCC TCB Certification ProcessFCC Certification through an accredited Telecommunications Certification Body (TCB) is mandatory for all intentional radiators.](/guides/fcc-tcb-process) * [ISED Canada CertificationComplete guide to ISED (Innovation, Science and Economic Development) Canada equipment certification: IC ID format, RSS standar…](/guides/ised-canada-certification) * [FCC KDB GuideThe FCC's Knowledge Database (KDB) publishes official guidance on FCC equipment authorization rules and test procedures.](/guides/fcc-kdb-guide) * [CE Marking for Unintentional RadiatorsUnintentional radiators — digital devices that generate RF as a byproduct of operation — must comply with the EU EMC Directive.](/guides/ce-marking-unintentional-radiators) * [FCC Part 15 Class B Emission LimitsFCC 47 CFR Part 15 Subpart B Class B digital devices: the exact radiated and conducted emission limits, the SDoC vs TCB authorization decision, accredited lab requirements, and the design strategies that buy reliable compliance margin.](/guides/us-fcc-part-15-class-b) Educational resource only. FCC regulations change and product-specific determinations depend on actual design and distribution. Verify current rules and obtain qualified engineering review before submitting for authorization.