There are several different types of keyboards, generally separated by the type of switch technology that is used. A switch is what a keyboard uses in order to register keystrokes, and alert the computer that a key has been pressed. This blog will outline the most common types of switches, and how they are used in keyboards on the market today.
A mechanical-switch keyboard uses individual key switches, located under each individual key cap. These are "clicky" keyboards that are louder than the average keyboard. Some people prefer not to use mechanical-switch keyboards in quiet office environments, but these switches are highly durable and are preferred by many people. The actual switch allows you to fully feel when a key has been pressed; offering a feel that makes you aware whether or not the key has been pressed and registered. If by chance a key goes bad, that individual switch can be replaced, and the keyboard can quickly return to normal use. Two common types of mechanical-switches are ALPS switches and Cherry switches. Mechanically speaking, this type of keyboard allows the fastest typing, as the switches "pop" up quicker than any other type of key switch.
Membrane Keyboards are the most common in today's market. Membrane keyboards are unlike mechanical-switch keyboards in that the entire keyboard operates on the same membrane (not individual switches for each individual key). Three flat membranes cover the entire keyboard, and underneath each key is a rubber dome. When a key is pressed, the dome is pressed down, and creates contact with the lowest membrane, creating a short circuit which sends the signal the the computer as a keystroke.
These keyboards are typically the most inexpensive, and have more of a soft feel that other "clicky" keyboards. They also provide the quietest keys for office settings. However, membrane keyboards do not offer very high durability, and over time suffer from decreased performance as the rubber domes may because inelastic or over-elastic. These keyboards generally cannot be cleaned or repaired easily, and typically need to be replaced when they go bad.
Diagram of a membrane key:
Scissor-switch Membrane Keyboards
Scissor switches are typically used in laptop computers and some other desktop keyboards. These keyboards use a membrane with rubber domes like regular membrane keyboards, but these switches have a scissor-like mechanism that both stabilizes the key and provides a bounce-back feel. The mechanism attaches to a plunger that depress the domes on the membrane, cutting down on the travel distance of a keystroke, so the keys do not need to be pressed down as far. These keyboards are much more durable than normal membrane keyboards, but still not as durable as the mechanical switches. While these keyboards are more expensive than membrane keyboards, they are of much higher quality, but still cheaper than the highest quality mechanical switch keyboards. They do not produce much noise either, and are comparable to the membrane keyboards in this area. They are a great cost-efficient alternative to the mechanical switches.
Diagram of a scissor-switch:
These are the switches immortalized by the IBM Model M and the older "clicky" keyboards. These keyboards are often mistakenly called mechanical switch keyboards, but in fact they are quite different. These switch utilize a spring that when pressed down, causes a small hammer to strike the rubber dome membrane. Many people prefer these switches as the spring provides more force feedback the further down the key is pressed. The picture below will demonstrate how it works.