Keyboard Construction and Operation

In general terms, the operation of a PC keyboard is fairly simple: you press keys on the keyboard, causing an electrical connection to be made. This causes the keyboard to send a signal to the PC, telling it what key or keys were pressed. Fairly simple stuff, at least in theory.

You might be surprised, however, just how much complexity is involved in allowing these signals to be sent to the PC--there is a lot going on "behind the scenes". You also might not realize just how many different ways there are to make the central components in the keyboard, or how many design issues must be taken into account in making a good keyboard. These design characteristics are what determine the critical comfort and feel factors that make you prefer one keyboard over another. They also dictate the durability and hence longevity of the keyboard.

In this section I describe the construction and operation of the keyboard. I start with sections covering the two most important sets of parts in the keyboard: the keycaps and the keyswitches. I then describe the other physical components that make up the keyboard. Finally, I talk about the actual operation of the keyboard, including the internal circuitry of the keyboard and how it interfaces to the rest of the PC.

When I disassembled the original PC/XT keyboard I got from a friend,
upon removing the bottom circuit board, all the little spring-loaded clips
that are used to provide tactile feedback for each key sprang loose. This
is one reason why I don't recommend disassembling your keyboard. :^)

Warning: As you read this description of keyboard technology, you might be tempted to disassemble your own keyboard to see the parts and discover how they work. If you are very careful and proceed slowly, you will probably be OK. Be forewarned, however, that keyboards in general are the "Humpty Dumpty" of PC components: some types, if you disassemble them too far, can come apart into hundreds of small pieces, and well, "all the king's horses and all the king's men…" You know the drill. :^) Even something as simple as removing a special keycap such as the one for the <Space Bar> can lead to great frustration trying to replace it.