其实准确的说
Class A和Class B的定义：
Class A digital device－A级数字装置
A digital device that is marketed for use in a commercial, industrial or business
environment, exclusive of a device which is marketed for use by the general public
or is intended to be used in the home.投放市场供在商业、工业或商务环境中使用的数字装置，但不包括投放市场供一般公众或家庭使用的装置。
Class B digital device－B级数字装置
Class B digital device. A digital device that is marketed for use in a residential
environment notwithstanding use in commercial, business and industrial
environments. Examples of such devices include, but are not limited to, personal
computers, calculators, and similar electronic devices that are marketed for use by
the general public. Note: The responsible party may also qualify a device intended
to be marketed in a commercial, business or industrial environment as a Class B
device, and in fact is encouraged to do so, provided the device complies with the
technical specifications for a Class B digital device. In the event that a particular
type of device has been found to repeatedly cause harmful interference to radio
communications, the Commission may classify such a digital device as a Class B
digital device, regardless of its intended use。
投放市场不仅供在商业、工业或商务环境中使用而且要在居住环境中使用的数字装置。这类装置的例子包括（但不限于）：个人计算机、计算器以及其它投放市场供一般公众使用的类似电子装置。注：职责部门也可以把投放市场以供商业、工业或商务环境中使用的装置定义为B级装置；事实上FCC也鼓励这一举措，只要该装置能满足B级装置的技术规范。若某类型装置反复地对无线电通讯产生有害干扰，则FCC可能会将之归为B级数字装置而不管其用途如何。
下面是
Subpart A – General（一般要求）
Subpart B - Unintentional Radiators（无意辐射体）
Subpart C - Intentional Radiators（有意辐射体）
Subpart D - Unlicensed Personal Communications Service Devices
Subpart E - Unlicensed National Information Infrastructure Devices
Subpart F – Ultra-Wideband Operation
Subpart G – Access Broadband Over Power Line (Access BPL)