The radios that fill a modern home — Wi-Fi access points, Bluetooth earbuds, cordless devices, garage-door openers — share something most users never think about: none of them required the owner to obtain a radio license. That is the work of FCC Part 15, the section of Title 47 of the Code of Federal Regulations that carves out a license-free regime for low-power devices. Part 15 is why you can buy a router and plug it in without filing anything, and it is also why that router occasionally drops a connection without recourse. Both halves of that bargain are written into the rule.

Section 15.1 states the scope. In the Commission's words, "This part sets out the regulations under which an intentional, unintentional, or incidental radiator may be operated without an individual license. It also contains the technical specifications, administrative requirements and other conditions relating to the marketing of part 15 devices." The three categories named there are the organizing structure of the entire part. An intentional radiator is a device designed to emit radio energy on purpose — a Wi-Fi or Bluetooth transmitter. An unintentional radiator emits RF energy as a byproduct of its internal digital operation without meaning to — a laptop or a digital television. An incidental radiator is not designed to generate RF energy at all but does so as a side effect, such as a motor. Part 15 governs all three, with technical limits scaled to each.

The defining condition of unlicensed operation lives in 15.5, and it is worth reading exactly, because it is the entire deal:

Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station, by another intentional or unintentional radiator, by industrial, scientific and medical (ISM) equipment, or by an incidental radiator.— 47 CFR § 15.5(b), source

No vested right to a frequency

Section 15.5 opens with a point that surprises people who assume buying certified hardware buys a claim to the airwaves. Paragraph (a) provides that persons operating intentional or unintentional radiators "shall not be deemed to have any vested or recognizable right to continued use of any given frequency" by virtue of prior registration or certification of equipment. The certification grant that lets a device be sold does not grant its owner a protected slice of spectrum. This is the legal underpinning of the everyday experience of a crowded 2.4 GHz band: a microwave oven, a neighbor's router, and a Bluetooth speaker can all share and contend for the same frequencies, and Part 15 devices have no standing to demand priority over one another.

The two obligations in 15.5(b) — cause no harmful interference, and accept whatever interference arrives — are asymmetric in an important way. The first is enforceable against the device: if a Part 15 device causes harmful interference to a licensed service, the Commission can require that the interference be corrected or the device be shut down, and 15.5(c) says the operator must cease operating the device upon notification that it is causing harmful interference. The second is a waiver: the device's owner accepts degraded performance as the price of license-free access and cannot complain when a higher-priority user disrupts the band.

Why the structure matters for products

Part 15's three-category structure maps directly onto how a product is authorized and labeled. Because intentional radiators carry the highest interference risk, they generally must go through the FCC's certification process and bear an FCC ID. Unintentional radiators — many computers and peripherals — typically qualify for the lighter Supplier's Declaration of Conformity path. The technical limits that a device must meet to qualify under Part 15 (emission limits, power limits, out-of-band restrictions) are spelled out in the part's later subparts and differ by category and by frequency band.

Section 15.1(b) closes the loop on what happens if a device falls outside these rules: operation of an intentional or unintentional radiator that is not in accordance with Part 15 "must be licensed pursuant to the provisions of section 301 of the Communications Act of 1934, as amended, unless otherwise exempted." In other words, Part 15 is an exception to the default rule that radio transmission requires a license. Stay inside the technical limits and accept the interference bargain, and a device may operate license-free; step outside them, and the device falls back into the licensed regime it was designed to avoid. That trade — unlicensed convenience in exchange for no protection and strict emission ceilings — is the foundation under nearly every wireless gadget in a consumer's home.

How the categories shape everyday devices

The three-category framework in 15.1 is not an abstraction; it predicts how specific products behave under the rules. Because an intentional radiator deliberately transmits, the technical subparts of Part 15 impose the tightest constraints on it — power limits, frequency restrictions, and out-of-band emission ceilings tuned to the band it operates in. A Wi-Fi access point and a Bluetooth speaker are both intentional radiators, and both are governed by band-specific emission rules layered on top of the general 15.5 conditions. An unintentional radiator such as a laptop is regulated not for what it transmits but for the digital noise it leaks: Part 15 sets limits on the radio energy its clocks and processors radiate as a byproduct, which is why even a device with no radio still bears an FCC compliance statement. An incidental radiator — a device with a motor or a mechanical switch that produces RF energy with no electronic intent — sits at the lightest-touch end, subject to the operating conditions but few specific technical limits.

This is also why the same band can feel both free and contested. The 2.4 GHz band that carries much consumer Wi-Fi and Bluetooth traffic is shared by countless intentional radiators, none of which holds the "vested or recognizable right" that 15.5(a) explicitly withholds. The rule does not assign households slices of spectrum; it lets compliant devices contend for the same airwaves and obliges each to accept whatever interference results. The practical experience of a slow connection in a dense apartment building is, in regulatory terms, exactly what Part 15 contemplates — many license-free devices coexisting under a bargain that guarantees access but not performance. Understanding that the convenience and the congestion are two sides of the same rule is the clearest way to read what Part 15 actually does for, and to, the wireless devices that fill a modern home.