Raspberry Pi A, Руководство пользователя, Страница: 224 / 314

P A R T I V
H A R D W A R E H A C K I N G
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There are also five-band resistors. You read these in the same way as a four-band resistor,
except that the first three bands offer resistance figures, the fourth the multiplier, and the
fifth the tolerance.
Sourcing Components
If you haven’t dabbled in electronics before, it can be difficult to find components and tools.
Thankfully, there are plenty of online and offline sources that specialise in the hard-to-find
components you might need to complete your project.
Online Sources
Two of the largest retailers of electronic components and tools in the world are
RS Components
and Farnell . Both operate offices and warehouses across the world, and both have a substan-
tial selection of hardware from which to choose. Chances are you’re familiar with at least one
of the two retailers. At the time of this writing, RS Components and Farnell were the only
two companies licensed to produce the Raspberry Pi hardware by the Raspberry Pi
Foundation, so unless you’re reading this book while considering the purchase of a Raspberry
Pi, you’ll have ordered the device from one of the two.
Both RS Components and Farnell focus on business-to-business transactions, meaning that
their main source of income is from electronics companies buying large quantities of compo-
nents. However, both will happily allow consumers to register with their respective web
stores and place orders as small as individual components.
When you’re placing small orders, be aware that there may be additional charges incurred. RS
Components charges for its next-day delivery service, and while the charge is quite reason-
able for larger orders, it can cost significantly more than the components being purchased
for smaller orders. On the other hand, Farnell doesn’t charge for next-day delivery but does
mandate a minimum total value for orders placed through its website.
Depending on where you live, you may be able to reserve items for collection at one of RS
Components’ or Farnell’s trade counters. This saves on the cost of postage and gets you the
goods faster, but it may not be an option at your location. The websites for both retailers can
be found here:
RS Components:
http://www.rs-online.com
Farnell:
http://www.farnell.com