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What is AT (Advanced Technology) Keyboard?
An AT keyboard or an Advanced Technology keyboard basically refers to the keyboard with the PC AT. Also known as the Model F keyboard, this is actually the US standard keyboard.
Technically, an AT keyboard signifies the keyboard that uses an AT or Din 5 port.
- The AT keyboard was launched in 1984 with the PC AT and in 1986 by IBM. Originally, this keyboard had 84 keys but was improved later on to include other keys into it totaling up to 101 keys.
- The keyboard design and keys included or excluded are also quite unique in this keyboard with the backspace, shift key and Enter key notably different in comparison to the other regular keyboards.
- To use an AT keyboard with the modern computers of today you will need to use an AT to PS/2 connector along with a PS/2 to USB male connector.
Understanding AT (Advanced Technology) Keyboard
Typically, any keyboard that uses the legacy 5 pin Deutsches Institut für Normung or DIN port is called an AT keyboard and is referred to as a 101-key enhanced keyboard.
This specific port standard was typically used in 1981 with the first IBM PC and in 1984 with the 2nd generation IBM AT.
Apart from PC keyboards, this connector was also used for several analog audio connections.
It was however replaced thereafter in 1987 on the IBM PS/2 with a Mini DIN connector which was smaller in size but had 6 pins in it.
These connectors were also used in the laptop computers for the first time.
An AT-to-PS/2 adapter will allow using newer keyboards with old computer models and vice versa.
Usually, the unique features of this particular type of keyboard in comparison to the newer keyboards are:
- It does not include the three extra Microsoft Windows keys found in various IBM compatible keyboards
- The Enter and left Shift keys are quite large as compared to the previous PC/XT keyboards
- The backspace is smaller.
The AT keyboard originally had only 84 keys and succeeded the XT keyboards that had 83 keys.
Moreover, the AT keyboard typically uses a different scan code and communication protocol.
AT Keyboard Port
As said earlier, the AT keyboards use the 5 pin DIN port. The different pins arranged in a semicircle in it had different purpose to serve such as:
- Pin 1 is for the keyboard clock
- Pin 2 is for the keyboard data
- Pin 3 is for the keyboard reset and is usually not used
- Pin 4 is for ground and
- Pin 5 maintains the constant voltage of +5 volts.
The DIN 5 port is however not commonly used today because most of the keyboards come with either a USB port or a Personal System/2 or PS/2 port.
Ideally, the Personal System/2 port is referred to as the keyboard or mouse port developed by IBM and is usually found at the back of the computer.
The port to connect the keyboard is usually purple in color and that dedicated for connecting the mouse is normally teal blue in color, which looks green.
If it is half purple and half green it indicates backward compatibility and will support either a PS/2 mouse or a PS/2 keyboard.
The PS/2 plug is male and the PS/2 port is female and the 6 pins in them comes with the following specifications:
- Pin 1 maintains a voltage of +2.0 volts to +5.5 volts and is assigned to carry keyboard data
- Pin 2 maintains a voltage of +4.8 volts to +5.5 volts and is reserve
- Pin 3 is the ground pin
- Pin 4 maintains a voltage of +2.0 volts to +5.5 volts and assures that there is +5.0V DC
- Pin 5 is assigned for keyboard clock and maintains the same voltage and
- Pin 6 is reserved and also maintains the same voltage.
There are also a few old keyboards connected to an AT port which is slightly bigger than a PS/2 port and therefore these cannot be used with modern computers. However, the PS/2 port and USB male connector will not work.
You may need to use an AT to PS/2 for the necessary conversion of signals but if the computer does not support a PS/2, you will need to further convert PS/2 to USB.
As you can see, the AT keyboard is quite different from the standard keyboards and also has some specific requirements to use in modern computers.
However, this US standard is not extensively used due to its different pin requirements, key inclusions and exclusions.