( COMPUTER LESSONS-5)
Key switches
To understand a keyboard, you must first understand the kinds of switches that are used. A computer keyboard is effectively an array of switches, each of which sends the PC a unique signal when pressed. Two types of switch are commonly used: mechanical and rubber membrane.
Mechanical switches; are simply spring-loaded "push to make" types, so when pressed down they complete the circuit and then break it again when released. These are the type used in click keyboards with plenty of tactile feedback.
Membranes switch; are composed of three sheets: the first has conductive tracks printed on it, the second is a separator with holes in it and the third is a conductive layer with bumps on it. A rubber mat over this gives the springy feel. When a key is pressed, it pushes the two conductive layers together to complete the circuit. On top is a plastic housing which includes sliders to keep the keys aligned.
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