Recognize and Fix Faults in Notebook: how to understand and rocognize fault in laptop, notebook. First complete guide (Italian Edition) by Davide Scullino & Roberto beneduci

Author:Davide Scullino & Roberto beneduci [Scullino, Davide]
Language: ita
Format: azw3, pdf
Published: 2014-07-26T04:00:00+00:00

The keyboard

It is the element with which the user introduces the data or answers to questions which the PC asks you to answer in order to proceed with the calculations in progress, has been and still is an indispensable element to the relationship between user and machine, because it serves to write text, to introduce numerical data and codes when required, not to mention that virtually all programs for Microsoft Windows and MacOS provide keyboard shortcuts, ie those key combinations that give immediate access to commands otherwise be given passing by the opening of one or more menus.

The development of the Personal Computer required to grow the keyboard to issue commands directly to some of the most exploited menu; here is that, from the first keyboards XT has passed to the 102-key with numeric keypad (for AT) to to the modern, which functions can be selected directly from the buttons such as Windows, menu, Alt Graph. The first is to open the Start menu (Start) and the other the context menu inherent to the position of the mouse pointer. as the Alt graph, activates certain characters such as @ for e-mail addresses and Internet the Euro symbol.

In laptops as in desktop PCs, there are buttons for the direct opening of Internet browser or the activation of the voice in voice- modem, but also for putting into standby (sleep) on the computer and the subsequent resumption of normal activities (Wake Up).

The keyboard is handled by a Keyboard Encoder, ie a coder that reads the pressure of the individual keys, arranged in a matrix and each generates a byte, so the key codes and characters are modular keyboard 256. The encoder output is read by the Southbridge chipset, so if more keys do not work you have to first see if it is a problem of a whole row and then go and check the conditions of Southbridge (the encoder does not fail almost never).

The keys on the computer keyboard are buttons that can be magnetic or electro. Are of the first type keys with Hall effect, which is used in computer keyboards fixed a few years ago and were very valuable (and unfortunately expensive...) because it is less subject to failure of those traditional electromechanical contact: in fact, the pressure the key in these devices is detected by the passage of the stem of the button in front of a magnetic sensor, since there are parts in contact, the closure of the keys do not depends on the wear.

The electric keyboards instead rely on a contact that is made to touch one below when you press the corresponding button; for this reason, as simple and economical are subject both to the consumption of the electrodes, both the oxidation of the same, which can lead to elevate the contact resistance to the point that no longer recognizes Keyboard Encoder button closure. The keyboards of this kind are essentially composed of many push button switches as there are keys that compose them.

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