Comparison Logitech Wireless Touch Keyboard K400 Plus vs A4Tech KV-300H

— Wired. Connection using a cable with one or another type of connector — most often USB, less often PS/2 or a proprietary plug (see "Connection interface"). Wired keyboards are notable for their low cost and overall convenience — in the sense that they do not require batteries and the operating time is unlimited. However the wire limits mobility; however, given that most often the keyboard is used in close proximity to the computer, this shortcoming cannot be called critical.

— Radio. Wireless connection over the air, usually through a wireless adapter connected to a computer via a USB port. The main advantage of this option can be called the actual absence of a wire; while the communication range is usually several metres, which gives freedom of movement and even allows you to use the keyboard as a "computer remote control". On the other hand, wireless models are much more expensive than wired ones, and their operation requires separate power supply from batteries or a rechargeable battery, the charge of which is limited — accordingly, the continuous operation time is limited. Separately, we note that this option is designed mainly for stationary PCs; if a wireless keyboard is needed for a laptop, it is better to pay attention to Bluetooth models (see below).

— Bluetooth. Another way to wir...elessly connect keyboards. Technically, Bluetooth is based on radio waves, but this technology has its own characteristics, so it is listed separately from the "normal" radio connection (see above). The main one of these features is that many models of modern electronics (almost all laptops and tablets, some PCs, etc.) are equipped with built-in Bluetooth modules, which allows you to connect such keyboards without using additional adapters. In addition, the range of such a connection is officially at least 10 m (in fact, of course, it depends on obstacles, interference, etc.). It is this option that will be optimal if you need a wireless keyboard for a Bluetooth-enabled device.

— Bluetooth / radio. Wireless keyboards that can connect both via Bluetooth and radio. See above for more details on each of these options. Also note here that such a keyboard is usually connected directly to a Bluetooth device (for example, a laptop), and if the computer does not support Bluetooth, you can connect a USB adapter to it and use a radio connection. Thus, the keyboard is as versatile as possible in connection. However, such versatility significantly affects the cost, and is required not so often; so this option is not widely used.

— Bluetooth / radio / wired. Keyboards that support all three connection methods described above. This is the most versatile option, giving the user the freedom to choose for different situations. For example, while playing a game or watching a movie, you can sit in a comfortable chair away from the screen by connecting the device wirelessly, and when typing or surfing the Internet, you can move to the table and use the wire, saving battery power. At the same time, such versatility is not often required and is expensive, so models with this type of connection are not popular either.

The length of the cable that the keyboard is equipped with for wired connection (see "Connection type").

When choosing this parameter, you should first of all take into account the distance from the device to the connection port: a cable that is too short may simply not reach the connector, and a cable that is too long may get confused at hand and create inconvenience. As for specific values, the reference length is 1.8 m. However, there are cables both shorter and longer.

The range of the wireless connection provided by the keyboard (see "Connection Type").

Almost all modern wireless models work confidently at a distance of at least 2 - 3 meters. So you need to pay attention to this parameter mainly when the keyboard is planned to be used at a greater distance from the computer. At the same time, when evaluating the range, it should be borne in mind that it is indicated for ideal conditions: the absence of interference and obstacles in the signal path, the battery is fully charged, etc. In practice, the communication range may be somewhat less, so when choosing, it is worth taking a certain margin. Nevertheless, according to the declared range, it is quite possible to evaluate the practical capabilities of different models and compare them with each other.

Traditional keyboards are divided into three main varieties — full-size, compact and ultra-compact. The main difference between them is that full-size models have a Num-block — an additional block with numeric keys and arithmetic signs. Compact models, respectively, do not have a num-block, and in ultra-compact models, the arrow block is either completely absent or located under the Enter key in the form of very small keys.

And full-size, and compact, and ultra-compact keyboards can have different types of layouts. At the same time, the arrangement of letters and numbers above the letters in all types of layouts is the same, the differences are in the shape and position of additional keys (special characters like backslash, system control, modifiers like Shift and Alt, etc.). Here are the most popular options:

— ANSI. The "American" layout format, the distinguishing features of which are, in particular, the same width of both Shift keys, the same labeling and assignment of the Alt keys, the single-row Enter key and the backslash located above it (which is often made slightly longer than the standard key).

— ISO. "European" layout format. The Enter key occupies two rows, while at the top it is slightly longer than at the bottom; the left Shift is shorter than the right one, ther...e is a backslash next to it; next to the bottom of the Enter may be a second backslash or other special character key; the right Alt is designated as Alt Gr and is intended for entering additional characters in European languages.

— K.S. The "Korean" keyboard layout provides a double-row Enter, as in the ISO described above, however, in this case, the lower part of the Enter is made longer, and not the upper one. The backslash is above Enter, next to Backspace, and Backspace itself is the same length as standard keys (that is, noticeably shorter than in other layouts).

— JIS. Keyboards with a "Japanese" layout have a double-row Enter with an increased length of the upper half — like the ISO described above. However, in this case, the backslash is not located on the left side of the keyboard, but on the right, next to Enter (where an additional symbol key can be located in ISO). Additional character keys may be provided — next to Backspace (as in KS) and/or to the left of the right Shift. In addition, the right Alt can be formatted as Alt Gr.

In addition to compact and full-size, there are also non-traditional keyboard formats:

— Num-block. Separately made block of numeric keys. With the help of such a device, you can, in particular, turn a compact keyboard into a full-size one. Among other things, this combination can be useful for travel: packing a Num-block separately from the keyboard is easier than finding a place for a full-sized "board". Another option for using the Num-block is to connect to a cash register, terminal, etc. to work as a calculator keyboard or in a similar capacity.

— Keypad. A specialized device in the form of a small (approximately 15 – 20 keys) keyboard under one hand; usually, it is complemented by an arm rest, and often also by side buttons for the thumb. Such devices are especially convenient for games and are mainly used in them — certain game actions can be attached to the keypad buttons (including those that are usually implemented through the menu or a key combination on a standard keyboard). The keypad can both complement the main keyboard and serve as a completely separate game pad.

— Non-standard. Non-standard format keyboards that do not belong to any of the varieties described above. The specific design and use of such devices may vary. So, these can be game models in the form of the left half of a standard keyboard (this part is mainly used in games); ultra-compact models for tablets (see "In the direction"); keyboards for TVs, supplemented with special buttons and designed to be held in two hands in the manner of a gamepad, etc.

— Classic type. Keyboard with keys of the usual square and rectangular shape, with a small distance between them. Such keys usually expand downwards so that the gaps between them are as small as possible.

— Island type. Also known as "soaring" or chiclet. This is a keyboard in which each key is installed in a separate hole at a small distance from the others. Island models are more convenient than classical ones in that they are less likely to accidentally press the adjacent key. On the other hand, they are more difficult to clean: debris that has clogged into the gap between the key and the “board” itself is quite difficult to clean out, while contamination can create problems in operation.

On the practical side, the choice of a particular type of keys depends primarily on the personal preferences of the user.

— Membrane. The name of this type is due to the fact that the contacts under each key are made in the form of two membranes — conductive disks on a flexible film. The return of the keys to their original position after pressing is ensured by the elasticity of the membranes. This design is characterized by low cost and low noise level; in addition, such keyboards are quite resistant to liquid spills (although this is still not recommended). Of the shortcomings, it is worth noting the relatively low durability — 3-4 times lower than that of mechanical ones. In addition, as the keys of this type wear out, the force required to press decreases, they begin to “fall through” under the fingers (“fatigue effect”).

— Mechanical. In this design, springs are used to return the key to its original position after being pressed. Mechanical keyboards are considered more advanced than membrane keyboards: they are more reliable and durable, almost do not lose properties as they wear out, and give a clear tactile feedback. The overall noise level is often higher than that of membrane ones, however, many attribute a characteristic click with each press to the advantages of such models; in addition, completely silent mechanical switches are also available. But of the unequivocal disadvantages, one can name the high cost and sensitivity to spilling liquid (although a mechanical keyboard can also be made waterproof)....r>
— Optical-mechanical. A variation of the mechanical keyboards described above, in which each key is equipped not with a traditional pair of contacts, but with an optical switch in the form of a sensor that receives an infrared beam; when you press the key, this beam is blocked, which serves as a signal for operation. One of the key advantages of such switches is a very high response speed (fractions of a millisecond); this moment is not critical for domestic use, but it can be fundamental for gamers-enthusiasts and e-sportsmen. In addition, the absence of electrical contacts that are prone to wear and oxidize has a positive effect on durability. And although initially the “optics” are more complicated than classic systems with contacts, however, in gaming keyboards, optical-mechanical switches are often even cheaper than pure “mechanics”. And the fact that this option is relatively rare is primarily due to the fact that optical technology appeared not so long ago and is only gaining popularity.

— Membrane + mechanical. A layout in which most of the keys have a membrane design, and some, the most "responsible" ones, are mechanical. About the features of both options, see above, and a similar combination of them is found mainly in gaming keyboards. In this case, the "mechanics" are usually used on the traditional combination of WASD plus on the surrounding keys Q, E, R and F.

— Mechanical-membrane. A hybrid design that combines elements of mechanical and membrane keyboards (see above for more on both). In this case, these features are combined in each individual key. Usually, under each button in such keyboards there is a membrane, however, inside this membrane is not just a pair of contacts, but a mechanical spring system. Thus, this design combines the advantages of both options. At the same time, mechanical-membrane systems are very expensive. Therefore, their main scope is high-end gaming keyboards, and even among such devices this option is quite rare.

— Scissor. A slightly modified version of membrane keyboards (see the relevant paragraph), in which the flexible membrane on each key is supplemented by a two-piece mechanism fastened together in the form of scissors. One of the main features of scissor keyboards is the low key travel (noticeably lower than that of membrane keyboards). Also, this design is less demanding on accuracy, it allows you to achieve a clear pressing regardless of where the finger hit — in the centre or on the edge of the key. The service life of the "scissors" is large; they are more difficult to clean, however, they become dirty much more slowly than "membranes". Among the disadvantages of this option, a slightly increased noise level during operation can be noted — due to the clicking of scissor mechanisms.

The number of additional keys provided in the design of the keyboard.

Such keys do not belong to the standard layout and are intended for quick access to specific functions or individual applications — for example, to control the media player or open mail with one click. This function is convenient because commands from additional keys are usually recognized by the system regardless of what is on the screen — thanks to this, for example, you do not have to close the text editor to switch tracks in the player.

Note that in this case we are talking about individual keys that have a strictly defined purpose and corresponding markings. Programmable buttons, the Fn key (see below) and the functions of the main keys implemented through Fn are not taken into account in this paragraph.

The presence on the keyboard of the Fn key(short for function). It belongs to modifiers, similar to Shift or Ctrl: by itself it does not perform any action, but when pressed simultaneously with another key, it changes its original purpose. Fn is often found in compact keyboards (see "Format"), but can also be set in full-sized ones. The features it provides include quickly changing the screen brightness or sound volume directly from the keyboard, using the centre keys as a Num-block, launching individual applications, and so on. Specific features of using the Fn key depend on the keyboard model.

The colour of the Cyrillic letters printed on the keyboard.

This colour is usually chosen so that the letters are clearly visible. This point does not affect the functionality of the keyboard, and the choice in this case depends mainly on personal preferences. However, there is also a practical point: for inexperienced users who have not mastered touch typing, it is desirable that the letters stand out as much as possible against the background of the keys.

Transparent letters are a separate case — they are used in keyboards equipped with a backlight (see below), due to which such characters, when the backlight is on, are visible even in the dark.