答：其实准确的说 FCC Part 15 B应该是FCC Part 15 Class B（B级数字装置）。
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。
问题1：FCC的目录？
答：下面是FCC PART 15目录章节内容：
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 Inbation Infrastructure Devices
Subpart F – Ultra-Wideband Operation
Subpart G – Access Broadband Over Power Line (Access BPL)
问题3：有意辐射体和无意辐射体的定义
答：Intentional radiator（有意辐射体）－定义. A device that intentionally generates and emits radio frequency energy by radiation or induction. 通过辐射或感应的方式有意产生和发射RF（射频）能量的装置。
注：红外线设备（比如：红外线遥控器）因为红外线不属于RF（射频），所以它不属于有意辐射体。另外，如果红外线设备的clock frequency（时钟频率）小于9KHz，那么它也不需要FCC Doc测试；
如果clock frequency（时钟频率）大于9KHz，那么它需要FCC测试，必须符合FCC Part 15.209（Radiated emission limits.－辐射测试）
Unintentional radiator（无意辐射体）－定义. A device that intentionally generates radio frequency energy for use within the device, or that sends radio frequency signals by conduction to associated equipment via
connecting wiring, but which is not intended to emit RF energy by radiation or induction.有意产生射频能量供给装置内部使用或通过连线将射频信号传送给有关设备使用，但不是有意辐射或感应的方式来发射射频能量的任一装置。
