A Selective History of Part 15 of the FCC Rules

An Engineering Perspective

A vintage black-and-white photograph of a technician in a suit wearing headphones while operating a large, cylindrical early radio tuning coil on a wooden laboratory workbench

rom the time that Heinrich Rudolf Hertz first demonstrated the transfer of electrical energy from one antenna to another in the late 1880s, humanity has witnessed, observed, and enjoyed the fruits of electromagnetic radiated fields. The electromagnetic waves first produced by Hertz in his lab in 1886 were proof that James Clerk Maxwell’s 1864 theory of “electromagnetic waves” was correct.

Hertz published a series of papers in the last years of the 1880s that verified the characteristics of the “Hertzian Waves” with respect to frequency, amplitude, speed (velocity of light), and other physical parameters. Hertz never realized the practical importance of his discovery and did not explore the applications of the “Hertzian Waves,” which became known as “radio waves” over time.

However, many premier scientists of the day did recognize the importance of the discovery, including Guglielmo Marconi, Nikola Tesla, Edwin Armstrong, Lee DeForest, and many others.

Wireless telegraphy was the first commercial use of the “radio waves” proven to exist by Hertz. The Boer War in the late 1890s showcased the first military use of wireless telegraphy; both warring nations used it to communicate between the units of their armed forces in that war.

Experiments continued in the 1890s and early 1900s to extend the range of the “radio waves” until the first messages were successfully sent from Europe to the United States.

As radio technology developed, radios became more popular and more prevalent, leading to interference between radio transmitters. To control the interference, countries met to develop an agreement to control the interference since the radio waves did not recognize or respect country geographical boundaries. The result was a “Final Protocol” signed at the Berlin Conference in 1903 that stated that “services be organized in such a way as to avoid interference with other stations.” This agreement was further strengthened in a second agreement signed at the Berlin conference in 1906.

The first radio law passed by the United States was the Wireless Ship Act of 1910, which required ocean-going vessels to be equipped with “an efficient apparatus for radio communication.”

Titanic Disaster – 1912

Marconi successfully put radio stations on ships so that they could communicate with shore-based stations and with one another. Marconi’s company even installed radios on the RMS Titanic, which sank during its maiden voyage after hitting an iceberg on the night of April 14-15, 1912. However, despite the availability of this advanced technology, the Titanic could not communicate with the Californian, a ship only ten miles away. As a result, many lives were lost that could have been saved. (The radio operator on the Californian had gone to bed and shut his radio system off about one hour before the Titanic hit an iceberg).

The Carpathia, one of the ships that heard the Titanic’s SOS call and came to save the survivors of the Titanic, had to come from fifty-eight miles away, and it took several hours for it to arrive. Anyone thrown or left in the cold water after the Titanic sank did not survive long enough to be rescued. People in the Titanic’s lifeboats or left clinging to wooden pieces of furniture/fixtures were rescued by the sailors of the Carpathia.

As a result of the Titanic disaster, the U.S. Congress passed the Radio Act of 1912, which dictated that each ocean-going ship had to have a radio room that was in operation 24 hours a day. This same legislation put the Department of Commerce in charge of licensing radio transmitters in the U.S., which consisted primarily of maritime (ship radio stations) and amateur radio stations.

Commercial Radio – 1920s

In December 1921, only two wavelengths were set aside in the U.S. for radio stations intending to broadcast to a general audience. The first wavelength was 360 meters (833 kHz), and it was designated for “entertainment,” while the second wavelength was 485 meters (619 kHz) and could be used for “market and weather reports.” The number of broadcasting stations in the U.S. grew rapidly and, by the end of 1922, more than 500 stations were operating in the country. The number of reserved transmitting frequencies also grew until they filled the frequencies from 550 kHz to 1500 kHz in ten-kHz steps.

Radio Act of 1927

Interference problems and other administrative challenges that arose with the rapid expansion of commercial (broadcast) radio forced Congress to enact additional legislation that was published as the Radio Act of 1927. This act created the Federal Radio Commission. Its five-member panel was given the power to grant and deny licenses, assign station frequencies and power levels, and issue fines for violations associated with the 732 broadcasting stations then in existence.

Communications Act of 1934

To handle the increasing judicial and technical issues surrounding commercial amplitude modulated (AM) radio, Congress passed the Communications Act of 1934. This act abolished the Federal Radio Commission and transferred its power to the Federal Communications Commission (FCC). We still operate today under this 1934 Act which has been amended and added to many times.

Part 15 First Appears – 1938

In 1938, we see the first mention of low-power devices in Part 15 of the FCC Rules. FCC Chief Engineer, Ewell Jett, argued that if certain radio frequency emissions were sufficiently weak and short-ranged so as not to be considered measurable, they would not rise to the level of harmful interference. One example of a typical device meeting these requirements was a Philco Radio and Television Corporation miniature transmitter remote‑control device for its standard broadcast receivers. It was the company’s belief that the transmitter could be operated without a radio station license since it operated by using an individual’s own home radio to receive and retransmit the low-level signal.

After studying the device, the FCC proposed that the operation of low-power transmitters without a license would be allowed if they met proposed standards that were so low in amplitude that they could not interfere with interstate communications. The new rules were called “the Low Power Rules.” These new rules required the use of minimum power and precautions against interference, plus the radiated field was limited to 15 microvolts per meter (uV/m) at a distance equal to the wavelength divided by 2 pi. These rules were adopted in November 1938 and remained in effect for low-power communication devices until 1957.

Revision of Part 15 – 1949-1954

After World War II, low-power radio devices increased rapidly, and some of the newer devices were designed to use frequencies that were higher than the AM broadcast band. To address these new issues, the FCC instituted a proceeding in April 1949 to address an overall revision of Part 15.

It wasn’t until April 1954 that the FCC issued a Notice of Proposed Rulemaking (Docket No. 9288) in which low-power devices were divided into two categories: 1) incidental radiation devices in which the RF energy is generated as a by-product of normal operation; and 2) restricted radiation devices in which RF energy is generated deliberately. Based on replies from industry, the FCC released new rules in December 1955, which established a table of permissible radiation limits for all receivers operating (tuning) between 30 and 890 megahertz.

A second report and order in Docket No. 9288 was issued in 1956 and 1957. It addressed community antenna television receivers and low-power communication devices (miniature transmitters).

Part 15 in the 1960s and 1970s

With respect to Part 15, the 1970s will be known for the release of a proposal to limit electromagnetic emissions from computers. Computers were classified as incidental radiation devices, and they were covered by Part 15 requirements. But the computer manufacturers were not designing or manufacturing their computers to any emission criteria in the late 1960s and early 1970s.

Led by the Computer and Business Equipment Manufacturers Association (CBEMA), the computer industry started meeting with the FCC to discuss the technical situation. The leading computer manufacturer at the time was IBM, and the other major U. S. manufacturers were Control Data Corporation, Univac, Digital Equipment Corporation, Honeywell, National Cash Register (NCR), Burroughs, and Xerox. The meetings were usually attended by one EMC engineer from each company, except for IBM, which sent two engineers and a lawyer.

The FCC started the discussions due to an increasing number of complaints regarding interference to radio and TV signals from computers. As the number of home computers (personal computers) began to increase in the late 1970s, the meetings between the computer industry and the FCC became more frequent.

FCC Docket No. 20780, which was released in 1976 to address restricted radiation devices, was the vehicle the FCC used to develop the case for limits on emissions from computers.

The FCC said that…

“It was initiating this rulemaking proceeding because it had found that the general requirement for restricted radiation devices – section 15.7 – adopted in 1938 and carried over into Part 15 in 1948, were no longer suitable for the numerous devices now regulated by these rules. Therefore, it proposed to clarify and further define these requirements, to recognize and define certain specific devices and in a few cases, to establish new requirements.”

Based on the studies done and released by CBEMA, the FCC adopted new rules on digital electronic equipment (especially computers) in September 1979.

Computer Limitations on Interference – 1980s

An order adopted by the FCC in March 1980 made a few minor changes to the original rules on computers and moved the effective dates of the rules to October 1981 for new equipment and October 1983 for older equipment. Under the revised rules, manufacturers had the responsibility to design and build their computers to limit their electromagnetic emissions to satisfy the regulatory limits set by the FCC. In addition, warning statements had to be placed on the computer and in the accompanying instruction manuals concerning their interference potential.

The FCC rules for computers defined two different classes of equipment: Class A for commercial computers and Class B for personal/home computers. The limits for Class A equipment were three times more relaxed than those applicable to home computers (in technical terms, about 10 dB more relaxed), resulting in higher limits.

Telecom Certification Bodies (TCBs) – 1990s – 2000s

Another major impact of FCC Part 15 devices on society started in the last years of the 20^th century. FCC General Docket Report and Order 98-68 was released at the end of 1998. This Docket was further defined in FCC Publication Notice DA-00-1223, which was issued in August 1999. This Notice signaled the implementation of what were called Telecom Certification Bodies (TCBs), beginning in June 2000.

FCC Public Notice DA 99-1640 was released in 1999. It stated:

“FCC Provides Further Information on the Accreditation Requirements for Telecommunication Certification Bodies (TCBs). This Public Notice provided further information on the accreditation requirements for TCBs including information on the accreditation body, the National Institute of Standards and Technology (NIST) of the Department of Commerce. The Notice concluded that “TCBs will have a major impact on how equipment manufacturers get their products approved in the future. The telecom industry representatives are looking forward to faster turnaround times on their product approvals.”

TCBs are private industry-independent organizations that have been authorized under the FCC program to issue grants to electronic product manufacturers for the certification of specific types of telecommunication products covered under the program’s scope. This included Part 15 products such as computers and computer peripherals. The program began with 13 designated TCBs.

The importance of the TCB program was further enhanced by the release of ET Docket No. 03-201 (FCC 04-1665). One of the FCC Commissioners at that time had the following to say about the Docket:

Separate Statement of FCC Commissioner Jonathan S. Adelstein

Re: Modification of Parts 2 and 15 of the Commission’s Rules for Unlicensed Devices and Equipment Approval; ET Docket No. 03-201

“The development of wireless ISPs and the advent of so‑called hotspots using unlicensed spectrum has been one of the Commission’s great success stories over the last several years. I support this item because it continues our efforts to promote the development of unlicensed devices and services. The tremendous growth of WiFi in the 2.4 GHz band was facilitated by the licensing (or more appropriately the “unlicensing”) approach initially adopted by the Commission for this band. Part 15 of our rules allows manufacturers to develop technologies for the unlicensed-bands that anyone can use without a license. We must continue this policy approach so that we encourage as many avenues or technologies as possible for broadband and other important services to reach consumers, no matter where they live.

“My goal as a policymaker is to maximize the services and information that flow over our airwaves. A regulatory framework for innovation can provide the necessary conditions that support the growth and development of spectrum-based services, including continued use of the unlicensed bands. Such a framework functions in a manner akin to a greenhouse, in which plants are protected from the elements by a structure and are nurtured so that they can thrive on their own within it.

“I believe that in the NPRM adopted today, the Commission properly strives for such an approach to spectrum management. We want to enhance our existing Part 15 structure so that it continues to encourage the growth of the unlicensed industries, but also controls the elements, like minimizing interference that may impact existing and future operators. Just as a greenhouse can support different types of plant forms, our framework for innovation does the same – it must be flexible enough to accommodate all different kinds of technologies, such as those used with the latest antennas. Our framework does not choose which technology will survive, and which will not, but it must create an environment that allows the different seeds of technology to truly have an opportunity to grow and develop on their own. I believe that we have such an approach here, and I am optimistic that our framework for innovation will enable new technologies in the unlicensed space to continue to meet the public’s demand for broadband more efficiently.”

By 2015, the FCC had turned over all Certification testing to the TCBs.

Other 1999 FCC Actions

FCC Public Notice DA 99-890 was released in May 1999. The FCC’s Office of Engineering and Technology (OET) clarified certain procedures that allow manufacturers to market central processing unit (CPU) boards as separate components.

In its FCC ET Docket No. 99-231 – Notice of Proposed Rulemaking, the FCC amended Part 15 of its rules relative to spread spectrum devices. It proposed changing the rules for frequency hopping devices operating in the 2.4 GHz band with a maximum output power of 1 Watt to allow for wider operational bandwidths.

Wireless Devices

The rapid expansion of wireless devices (initially driven by the release of the Apple iPhone in 2007) proved that the FCC was forecasting the future demand of testing appropriately. The FCC, as a single source of testing, would not have been able to test all the new product designs released as a result of the wireless demand. However, industry responded with additional testing labs and TCBs to handle the avalanche of wireless products produced by the innovative electronics industry.

Summary

Part 15 – Low Power Devices continues to be an important part of the FCC Rules. Many clever innovations have resulted from the category of “unlicensed” products unleashed on society by smart and hard‑working electronics engineers. The FCC has responded by opening new swaths of spectrum at higher and higher frequencies to allow the development of additional devices with expanded capabilities. The FCC has worked closely with TCBs to ensure the effectiveness of the Part 15 Rules, including informal rulings called KDBs (for Knowledge Database) guidelines for qualifying products to the FCC Part 15 Rules.

Bibliography

E. W. Allen, Jr., and Herman Garlan; “Evolution of Regulatory Standards of Interference,” Proceedings of the IRE Professional Group on Radio Frequency Interference; 18 August 1961.
“FCC and Electrical Interference,” Interference Technology Engineers’ Master (ITEM) 1977.
Art Wall, “Understanding FCC Regulations for Computing Devices,” 1980.
“Federal Radio Commission,” Wikipedia, 2025.
“FCC Proposes Rule Amendments for Radio Frequency Devices (Docket 20780),” News – FCC – Report No. 11843 – Action in Docket Case – April 20, 1976.
Kenneth R. Carter, “Unlicensed To Kill: A Brief History of the Part 15 Rules,” Vol. 11, No. 5, pages 8-18, 2009.
“Communications Act of 1934,” Wikipedia, 2024.

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Daniel D. Hoolihan is the founder and principal of Hoolihan EMC Consulting. He served as chair of the ANSC-C63 Committee on EMC from 2012 – 2022. He is also a past-president of the IEEE’s EMC Society, and currently the Chair of the History Committee for the EMC Society. Hoolihan is also an assessor for the NIST NVLAP EMC and Telecom Laboratory Accreditation program. He can be reached at danhoolihanemc@aol.com or at 651-269-3569.

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