# keyboards
a brief overview

# keycaps
form factor of the user-facing surface.
* surface profile: flat, cylindrical, spherical
* row shaping: flat, sculpted by row, tower-staggered
* height: ultralow, low, standard, tall
* family:
  * low-profile: reduced height, usually cylindrical or flat; optimized for thin keyboards
  * oem: medium height, cylindrical, sculpted by row; default for many mass-market boards
  * cherry: medium-low height, cylindrical, sculpted; compact vertical profile, widely used
  * sa: very tall, spherical, tower-staggered; retro aesthetic, heavy key travel feel
  * dsa: uniform height, spherical, flat rows; easily rearrangeable, consistent profile
  * xda: low height, wide tops, spherical, flat rows; uniform but with more surface area than dsa
* shaft depth: raised, flush
* material: abs single/double, pbt dye-sub/double, pom
  * pbt double-shot: durable, clear legends
* unit sizes (ansi):
  * 1u: letters, numbers, punctuation, ctrl, alt
  * 1.25u: bottom-row modifiers
  * 1.5u: tab, caps lock
  * 2u: numpad 0, numpad +, numpad enter
  * 2.25u: left shift
  * 2.75u: right shift
  * 6.25u: spacebar
  * others: 1.75u caps lock or right shift (compact variants)
* mount systems
  * stems (main interface):
    * cherry mx cross: dominant, widest compatibility
    * alps: legacy rectangular stem
    * topre: slider-over-dome, proprietary
    * scissor: dual-hinge, flat
    * optical/hall custom: varied, vendor-specific
    * pos mount: rectangular industrial form
  * stabilizers (large-key support):
    * none: standard for 1u keys
    * dual-stem: two functional stems (common in 2u keys, e.g. numpad 0)
    * single stem + support posts: one functional stem, plastic supports left/right
    * wire stabilizers: bar connecting to clips or inserts; used on spacebar, shift, enter

# switches
mechanism converting press to signal.

## types
* scissor: quietest, ultralow profile, short actuation depth, tolerant to angled presses; dominant in laptops and compact boards
* hall-effect: non-contact, analog depth sensing, highly durable, allows configurable actuation points
* cherry mx: canonical family, linear/tactile/clicky variants with wide ecosystem
* ultralow mx, standard mx, optical, membrane, capacitive

## mounting
* hot-swap: tool-less replacement
* soldered

## spring
* coil, leaf, torsion, none

## characteristics
* actuation type: linear, tactile (bump), clicky (bump + sound)
* actuation force: light (<45 g), medium (45-60 g), heavy (>60 g)
* actuation distance: 1-2 mm typical
* total travel: 2-4 mm typical
* durability: 50-100+ million presses
* acoustic profile: silent, quiet-damped, tactile, clicky

# layouts
arrangement and form of keys.

## standards
* ansi, iso, jis, custom
  * ansi: symmetric shifts, easier keycap sourcing, compact enter

## sizes
* 100%: function keys, arrows, numpad
* tkl (80%): function keys, arrows, no numpad
* 75%: arrows and function keys, denser
* 65%: arrows, no function keys, compact
* 60%: no arrows, no function keys, minimal
* <40%: reduced layers, often programmable

## purposes of extra keys
* arrows: text navigation, word skipping with modifiers
* function keys: shortcuts, system control, programming contexts
* numpad: efficient one-hand number entry, common in games and finance

# ergonomics
typing comfort.

* sculpted layouts: concave wells or height tiers
* split keyboards: halves separated, may reduce shoulder strain if matching shoulder distance
* arm rests: offset case height, prevent wrist extension
* compact/numpad-less: reduce lateral reach distance to mouse.
* flat-profile keys: allow angled presses, not as strictly vertical

# connectivity
interface and power.

* cable: usb-c, usb-a
* wireless: bluetooth, 2.4 ghz dongle. occasional re-pairing, pairing delays, and even transmission delays or signal obstruction are possible
* power: external (wired), internal rechargeable battery (battery will eventually fail or lose charge, regular charging necessary which may lead to critical need with insufficient charge)

# input performance
responsiveness and key detection.
* polling rate: 125 hz (8 ms), 250 hz (4 ms), 500 hz (2 ms), 1000 hz (1 ms), 2000 hz+ (sub-ms)
  * high polling (>1000 hz): gaming, esports latency reduction
  * standard (125-500 hz): sufficient for typing and general use
* key rollover: 2KRO, 6KRO, NKRO
  * 6KRO: common USB limit
  * NKRO: full simultaneous key detection, preferred in gaming/enthusiast boards

# noise
sources of sound during typing.

## causes
* bottom-out: stem hitting switch base
* top-out: stem slamming into housing when released
* wobble: lateral play of keycaps and stems
* case transmission: vibrations carried by keyboard chassis
* desk resonance: low-frequency amplification from surface coupling
* case weight: heavier cases reduce high-frequency sharpness, but do not prevent low-frequency desk resonance

## mitigation
* small-radius corner pads: most effective; isolate contact points, filter low frequencies, eliminate deep desk resonance, leave only intrinsic switch sounds
* switch lubing: reduces friction and spring noise
* case padding: foam inserts absorb vibration inside chassis
* broad foam mats: still low-frequency coupled to the desk

# use cases
optimum hardware depends on what the keyboard primarily triggers.

## text entry
* trigger type: discrete characters
* requirements: high rollover (>= 6KRO), low-profile or scissor switches, short actuation depth, consistent feel
* polling: >= 125 hz (500 hz optional, no benefit beyond)
* noise control: important in office/shared environments

## gaming - digital
* trigger type: discrete game functions
* requirements: low latency, high rollover (NKRO), durable linear or tactile switches, consistent reset
* polling: >= 1000 hz (higher rates unnecessary for digital keys)
* noise: less critical than latency

## gaming - analog
* trigger type: one-dimensional continuous (key depth mapped as analog axis)
* requirements: hall-effect or optical analog switches, adjustable actuation points, smooth travel
* polling: >= 1000 hz minimum; 2000–8000 hz improves depth granularity
* noise: secondary consideration

## special/industrial
* trigger type: macros, control codes, machine functions
* requirements: reliable switches (hall, capacitive), programmable layouts, rugged cases
* polling: >= 125 hz (standard sufficient)
* noise: often irrelevant

# typing systems
input methods and layouts beyond physical design.

## techniques
* 10-finger system: maximizes efficiency, reduces hand travel
* number row typing: allows 10-finger entry of digits, space-efficient alternative to numpad

## logical layouts
* qgmlwb and others: niche, maximize efficiency at cost of compatibility
* colemak: keeps many qwerty shortcuts; balances load across hands; smoother transition path
* dvorak: places common English letters on home row, but biased toward right hand; efficiency vs qwerty, less compatible
* qwerty: legacy, widespread, highest compatibility
see also [carpalx](https://mk.bcgsc.ca/carpalx/).

# brands
wooting (hall analog), lowfree, nuphy, keychron, mistel, varmilo, typematrix (matrix layout), kinesis (ergonomic split), cherry

# references
* cherry kc4000: compact scissor, discontinued