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In the discussion of the regulations throughout this chapter, a
distinction is made between intentional and unintentional radiators. A
spread-spectrum transmitter is designed to send out (or emit) an RF signal. This
(or any radio transmitter for that matter) is known as an intentional radiator. Intentional radiators emit
signals that are wanted (or intended for emission).
Although this chapter focuses on the intentional emissions of
802.11 transmitting devicesin other words, the radio energy produced to transmit
informationcertain regulations refer to unintentional radiators. Practically any
electronic device also emits unintentional RF emissions of some level of energy
that can impact the operation of other devices. Unintentional radiators are devices that emit radio
signals typically not designed for transmission. (These are, in most cases,
unwanted signals.)
These unintentional radiations are also subject to regulation.
In the FCC regulatory domain, the level of unintentional emissions falls into
two general categories: Class A or Class B. The FCC Class A device allows for a
higher emission amount, and regulations of this class apply to devices designed
for operation in industrial, office, and similar commercial environments. The
FCC Class B device must meet a more stringent standard that applies to operation
in residential environments and commercial environments representing a superset
of the two.
A similar set of dual standards exists in the European Telecommunication Standards
Institute (ETSI) domain, which falls under the Conférence Européene des Administrations des Postes et des
Télécommunications Administrations (translated to European Conference of
Postal and Telecommunications [CEPT]). The document #EN-55022 describes these
standards. ETSI follows similar naming conventions in that it has a Class A for
commercial use and a Class B for residential operation, although the classes do
not identically match the FCC Class A and Class B in terms of emission
allowances.
A common benefit
of 802.11 is that it enables users to have connectivity in a variety of
environmentshome, office, and even public areas such as hotels, airports, coffee
shops, and restaurants. Because these 802.11 devices are used in various types
of environments, they must comply with FCC Class B regulations. The 802.11 access point (AP) and bridge devices are typically
static, or permanently mounted, and can therefore be designed with a particular
operating environment in mind (residential or commercial). Oddly, the
higher-performance, higher-cost APs designed for operation in the enterprise are
subject to the more forgiving emissions
standard (Class A) than their lower-cost counterparts designed for installation
in the home. It is typical for enterprise-destined APs to be FCC Class B
certified, even though it is not an absolute requirementit just shows a
generally higher level of quality.
Almost all electronic devices, including 802.11 devices as well
as your computers, televisions, video game machines, radios receivers, and so
on, have a Class A or Class B rating. |
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