For my own future reference and because I think a weblog that rants about the web Reset buttons AND rates favorite goat cheeses needs to be shared: Sylloge.
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While making a 12vdc adaptor for my iPod I was digging through an old drawer of resistors (everyone should have one) and ran across resistors from the past.
Resistors, well, resist electron flow and are integral to all electronic circuits. Through the course of creating analog or digital device a designer will use a wide variety of resistors. Differing levels of resistance and power handling capabilities, higher power typically indicated by larger resistors.
The photo shows just a few of the styles you might encounter if you started digging around inside your electronic gear. The upper left resistor might be from an old tube type radio. The itty bitty square resistors held captive in the paper strip (there's seven of them) are surface mount resistors used in a development board at work but you're just as likely to find them in digital cameras, cell phones, and your computer.
The red resistor is the only one with text values printed on it. Most resistors have color codes to indicate their value and tolerances. Typical tolerances are from 5 to 20 percent and that's usually fine, but if needed they can be quite precise.
On the right, that thing with all of the dials, is a decade resistance box. Using dials that move in base ten steps (i.e. decade?) you can dial in a resistance. Wire the box into your design and you can tweak circuit resistance values in real-time. This was probably a more common aid back in the days of vacuum tubes. Back then a new-fangled "decade resistance box" may have reduced new product design by ten years.
You can still find decade resistance (and capacitance) boxes for sale.