science

Title 47 CFR Part 15

Title 47 CFR Part 15 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Title 47 CFR Part 15 rather than just read about it. In short: Code of Federal Regulations, Title 47, Part 15 (47 CFR 15) is an oft-quoted part of Federal Communications Commission (FCC) rules and regulations regarding unlicensed transmissions. It is a part of Title 47 of the Code of Federal Regulations (CFR), and regulates everything from spurious emissions to unlicensed low-power broadcasting.

Key takeaways

Title 47 CFR Part 15 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Title 47 CFR Part 15 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Title 47 CFR Part 15 from memory before moving on to harder problems.

Reference excerpt

Code of Federal Regulations, Title 47, Part 15 (47 CFR 15) is an oft-quoted part of Federal Communications Commission (FCC) rules and regulations regarding unlicensed transmissions. It is a part of Title 47 of the Code of Federal Regulations (CFR), and regulates everything from spurious emissions to unlicensed low-power broadcasting. Nearly every electronics device sold inside the United States radiates unintentional emissions, and must be reviewed to comply with Part 15 before it can be advertised or sold in the US market.

Subparts

A - General Subpart A includes 21 sections from 15.1 to 15.38. 47 CFR 15.1 states that any radiator (that which emits radio energy), whether or not intentional, must be licensed unless it meets 47 CFR 15 or is otherwise exempted by the FCC. 47 CFR 15.3 the definitions are defined by the definition given. 47 CFR 15.5 contains a general provision that devices may not cause interference and must accept any interference received. You are cautioned that any changes or modifications to devices not expressly approved by the party responsible for compliance may void your authority to operate devices. 47 CFR 15.5 prohibits intentional damped wave transmissions such as spark-gap transmitters which were common before the 1920s but occupy a needlessly wide range of frequencies. 47 CFR 15.9 prohibits operating a device under Part 15 for the purpose of eavesdropping, except when under lawful authority of law enforcement or when all parties in a conversation consent.

B - Unintentional radiators Subpart B deals with unintentional radiators—devices for which the purpose is not to produce radio waves, but which do anyway, such as computers. There are 16 sections between 15.101 and 15.123.

C - Intentional radiators Subpart C deals with devices that are specifically designed to produce coherent radio waves, such as small transmitters. Specific to broadcasting, 15.221 (and 15.219) deal with the AM band; & 15.239 deals with the FM band. 15.247 covers most Wi-Fi frequencies that aren't U-NII.

D - Unlicensed PCS devices Sections 15.301 to 15.323 deal with unlicensed PCS devices from 1.91 to 1.93 GHz. Cordless telephones using DECT 6.0 standards use this unlicensed PCS band.

E - Unlicensed NII devices 15.401 to 15.407 deal with unlicensed National Information Infrastructure (U-NII) devices

F - Ultra-wideband operation 15.501 to 15.525 deal with ultra-wideband (UWB) devices, including ground-penetrating radar.

G - Access Broadband over Power Line 15.601 to 15.615 deal with broadband over power lines (BPL) devices operating in the 1.705–80 MHz band over medium- or low-voltage lines.

H - Television Band Devices 15.701 to 15.717 deal with (TVBDs), TV-band devices that operate on an available television channel in the broadcast television band. An available channel is a 6 megahertz television channel that is not being used by an authorized service in a given geographical location, and thus may be used by unlicensed devices under the provisions of this rule part.

Subjects

Unintentional radiators Unintentional radiators are designated in two major classes:

Class A Device marketed for use in business/industrial/commercial environments. Class B Device marketed for use in a residential environment, notwithstanding use in industrial or commercial environments The emission limits for Class B devices are about 10 dB more restrictive than those for Class A devices since they are more likely to be located closer to radio and television receivers. These devices include personal computers and peripheral devices, and electrical ballasts for fluorescent lights.

Unlicensed broadcasting On the standard AM broadcast band, under 15.219, transmission power is limited by 100 milliwatts of DC input power to the final RF stage (with restrictions on size, height of, and type of antenna), or alternatively, under 15.221, if the AM transmission originates on the campus of an educational institution, the transmission can theoretically be any power so long as it does not exceed the field strength limits stated in 15.209 at the perimeter of the campus, 24,000/fkHz μV/m. Unlicensed broadcasts on the FM broadcast band (88 to 108 MHz) are limited to a field strength of 250 microvolts per meter (~48 dBμ) measured at a distance of 3 meters. This corresponds to a maximum effective radiated power of 0.01 microwatts. Emissions must be kept within the 88.0 to 108.0 MHz band under 15.239 rules. Unlicensed broadcasts on the TV broadcast bands are prohibited, except for certain medical telemetry devices, wireless microphones, and other low power auxiliary stations. 87.5 to 88.0 MHz is considered part of the VHF TV low band. For TV, 15.241 and 15.242 deal with high VHF (channels 7 to 13), 15.242 also deals with UHF (band IV and band V).

Common uses of Part 15 transmitters Frequently encountered types of "Part 15" transmitters include:

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Title 47 CFR Part 15

Start with the simplest possible case. Write down what Title 47 CFR Part 15 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Title 47 CFR Part 15 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Title 47 CFR Part 15 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Title 47 CFR Part 15

In research: Title 47 CFR Part 15 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Title 47 CFR Part 15 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Title 47 CFR Part 15 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Broadcast law, Code of Federal Regulations, Electronics and the environment, so understanding it makes those chapters shorter.
In everyday life: Look for Title 47 CFR Part 15 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Title 47 CFR Part 15 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Title 47 CFR Part 15 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Title 47 CFR Part 15 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Title 47 CFR Part 15 in simple terms?

Why does Title 47 CFR Part 15 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Title 47 CFR Part 15?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Title 47 CFR Part 15.