We’ve been doing some research into how we can sell our designs without needing FCC testing. There are a number of exemptions called out in CFR47 15.103.
One of the more interesting exemptions is the one related to “digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz.” We’ve read some discussion forums where some interpret this to include harmonics generated by the oscillator, which would make this exemption quite narrow in application. However, there is a FAQ page at bureauveritas.com that seems to interpret this to mean “digital devices oscillating below 1.705 MHz. See here (cached copy) Take note of the answers to the following questions:
- Can’t I be exempt from FCC regulations?
- What kind of digital consumer products get exempted?
I’ve sent them a message asking if they believe the harmonics are excluded under this exemption. I’ll update the post with their reply.
Update February 25, 2013
The response from Bureau Veritas is probably what you would expect: cautious with a slant for testing:
Digital devices using oscillator frequencies of 1 MHz (or even lower frequencies) are not necessarily exempt from FCC requirements. As you indicated, the potential for harmonics extending beyond 1.705 MHz exists, and these harmonics could conceivably emit at power levels that would require compliance testing.
Obviously, specific product design will ultimately determine the level of concern, but it is not a safe assumption that the oscillator frequency alone will define FCC exemption.