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link. Be very careful when using RF links. Make sure the transmission distances
are well known because RF signals degrade rapidly over distance. The control sys-
tem for the robot must be capable of surviving the interruption or corruption of the
data streams coming over the communication link.
Here are a few sites about 802.11 technology:
www.computer.org/students/looking/summer97/ieee802.htm
www.wave-report.com/tutorials/ieee80211.htm
www.homenethelp.com/802.11b/index.asp
www.80211-planet.com/tutorials/article/0,4000,10724_1439551,00.html
www.webopedia.com/TERM/8/802 _11.html
www.intelligraphics.com/articles/80211_article.html
Wireless Infrared (IR) IR light is another possible method of communicating
from place to place. IR exists in sunlight and everywhere in our daily existence.
It can give us sunburn and it’s just waiting to ruin the first robotic IR communi-
cation link it can find. Stray IR radiation is less prevalent indoors and has been
used indoors for low-speed data links over short distances. But even indoors, RF
communication links are beating the pants off IR communication links in all
respects. The TV clicker may be the only appliance still using IR inside most
houses.
Here’s a great site detailing much of the wireless LAN technology currently avail-
able: ftp://ftp.netlab.ohio-state.edu/pub/jain/courses/cis788-95/wireless_lan/
index.html.

PERIPHERALS
To round out our talk about I/O, let’s talk about peripherals. Although the use of periph-
erals involves data communication over communication buses and links, it differs in
some respects. Peripherals are often thought of as sources or destinations for data. They
are devices that are attached to the computer to allow the entry, storage, or display of
data. Peripherals are a bit boring and commonplace; they’re described in thousands of
articles. So why talk about them here?
First of all, robots are generally thought of as portable devices, clunking away their
existence in dusty, poorly lit industrial cubicles to satisfy the peevish desires of their
slavish masters. (Does this hit home? I hope I haven’t ruffled any feathers out there!)
Peripherals have to be carefully chosen if they are to match the requirements needed for
a robot. If the robot moves or vibrates, many new requirements must be addressed,
including vibration, shock, temperature, humidity, power reliability, and electrical radi-
ation. We’ll look at all these factors later as we consider environmental issues, but we
can take a look at some of the I/O peripherals in this chapter.