Alps SKCL/SKCM series
|This article requires illustration in the form of diagrams — need disassembly diagrams, and diagrams showing operation|
Alps SKCL/SKCM series, commonly referred to as complicated Alps, Alps Bigfoot, and Alps CM, switches, are the most common type of Alps switches used in computer keyboards. First introduced as early as 1984, the Alps SKCL/SKCM series has been one of the first commonly available, compact-design keyboard switches. Over the years there have been many variants of the keyswitch, including changes in colour and design. Early variants of the Alps switch did not carry the Alps logo on the top part of the case, and only had it stamped in on the switch bottom.
The terms "ALPS" and "Alps" are widely misused to refer to a large number of clone switches manufactured by other companies; although most clones are clearly different from genuine Alps switches, they are similar enough that many people fail to differentiate Alps switches from the copies.
Alps SKCL/SKCM series has gone by many names, owing to widespread misunderstanding. The term "bigfoot" was coined by MouseFan, and has largely fallen out of favour. "Alps CM" was coined from a misunderstanding of Alps part numbers and is not considered correct. "Complicated Alps" is not an official term, but it does serve as a convenient term to describe the SKCL/SKCM series, with a fairly high 10–13 parts per switch.
There is no known name or term that covers both complicated (SKCL/SKCM) and simplified (SKBL/SKBM series) switches. According to Sandy, 'SK' stands for "single key"; "SK" is used in the part numbers of many Alps switches. It is possible, but not confirmed, that the two switch series may be validly referred to as SKC and SKB respectively.
A useful mnemonic for dealing with Alps part numbers, is "L" for "linear" (SCKL and SKBL), and to imagine that the "C" in SKCL/SKCM stands for "complicated" (and possibly "B" for "basic" in SKBL/SKBM).
Alps SKCL/SKCM series is widely referred to as "complicated Alps", due to the design of the switch. SKCL switches have a fairly high count of 10 parts per switch, and the click or tactile leaf of an SKCM switch brings this to 11. The complexity comes from the switchplate, the assembly that contains the electrical contacts.
The switchplate contains two terminals, with a flexible metal foil membrane placed against the first, and held apart from the second by a plastic separator. This whole assembly is held inside a plastic plate, above which a sprung actuator leaf is fitted. The slider bends the actuator leaf back against the plastic plate, where it presses a flap against the foil membrane, which is pressed against the rear terminal.
The plastic block initially extended down to the base of the shell; this is a known as a "long" switchplate. Later switches had this plastic block reduced in height, leaving a gap between it and the bottom of the shell; this is termed a "short" switchplate. There has been speculation that reducing the length of the switchplate degrades the smoothness of the switch, but this seems unlikely. Short switchplates are supported by two small posts adjacent to the holes for the legs.
The colour of the switchplate has also changed twice. Early switches used the black switchplates from Alps vintage tee mount switches. The colour was soon changed to grey, with no other apparent change. Around 1987, the colour was changed again, to translucent white, which would be the final colour. The height was changed from long to short soon afterwards, around 1988.
On switches made up to 1993, the slider aperture contained a pair of prongs, one per side, possibly designed to dampen the impact of the return stroke. The resulting appearance of a switch shell with these prongs is described as "having slits", one above and one below each prong. These prongs, and thereby the slits, disappeared around 1993. MouseFan in particular considers the switch quality to have degraded around the time that the slits disappeared.
Early Alps SKCL/SKCM switches only bore the Alps logo on the bottom, where it could not be seen without removing the switch from the keyboard. Around 1988, Alps added their new-style logo the top of each switch, just after Alps SKCM White was introduced. At least two variants of this logo can be found, as Alps broadened the strokes of the letters. The old oval logo also disappeared from the bottom of the switch at some stage.
The lack of visible branding on older switches is one of the aspects of confusion between genuine Alps parts and clone switches, as most of those are completely unbranded.
Simplified Alps switches seem to have first appeared around 1996. Simplified Alps was a redesign of the switch to remove the complexity of the switchplate system. Instead of a switchplate, the actuator leaf is part of the front terminal, as with Alps clone switches.
When examining unbranded Alps-style switches on a keyboard, the key detail to look for is the number of side tabs that support the switch in the mounting plate. If the switch has four small tabs (a so-called "four-tab clone"), it is certainly a clone. If the switch has two long side tabs, it is relatively likely to be genuine Alps (especially if the board dates back to the 1980s), but there are copies of the switch with long tabs.
Four small tabs:
guaranteed to be a clone or derivative
Alps switches came in many colour variants, most of the time used to define the switch type. Despite being a pretty good rough guide, Alps did not always stick to their colour codes and seems to have changed colours randomly for reasons unknown. All of the colours listed below refer to the slider.
|White: The white Alps CM switch is one of the most common Alps switches. It is a clicky and tactile switch existing in both complicated and simplified variants. Early versions did not show the Alps logo on the top part of the case and seem to be identical to the older blue Alps switches. The newer variant, has a slightly different contact plate. The Alps logo uses flat lettering in the complicated version, and strongly raised lettering in the simplified version.|
|Black: The black Alps CM switch is a tactile, non-clicky switch, also in complicated and simplified variants. They normally have the Alps logo embossed on the top part of the switch casing. The most common keyboards utilising this switch are those from the Dell AT101 family. As with white Alps, the logo has flat lettering in complicated switches, and visibly raised lettering in simplified switches.|
|Blue: The blue Alps CM switch is the first switch of the CM series introduced to the mass market. It is a clicky and tactile switch. Blue CM switches generally do not have the Alps logo engraved on the top part of the switch case. This switch seems to have been mostly replaced by the almost identical white switch starting in 1987 or earlier. Some people believe the blue switch to be smoother in feel than the white one.|
| Cream (tactile): Off-white or pale yellow "cream" coloured sliders with rubber dampers that dampen both bottoming and release.
The most common keyboards utilizing this switch are the Apple Extended Keyboard II (M3501) and some keyboards from Silicon Graphics such as the "SGI Granite" (9500900). A less common variant of the switch has a white slider. At least one keyboard (the HP C1414A AT) has cream sliders without the dampers fitted.
Less common colours
|Green: Linear (with LED cutout); tactile (without LED cutout)|
|Grey (complicated): Linear, with LED cutout; in the region of 120 cN.|
|Grey (complicated): Linear with higher resistance, for space bars (with LED cutout)|
|Grey (simplified): Clicky. Alps-branded, but it remains unconfirmed whether Alps made these before Fuhua took over (see Fuhua Alps).|
|Grey (simplified): Tactile. Alleged to exist in some Strong Man SMK-85 keyboards; not confirmed.|
|Dark grey: Alps SKCL Lock, used for caps lock. Sighted with 'ALPS' embossed into the housing.|
|Cream (lock): Alps SKCL Lock|
|Salmon or Pink: Tactile. Sighted with 'ALPS' embossed into the housing.|
|Bright yellow: Linear, with LED cutout.|
|Taxi yellow: Clicky (without LED cutout) or linear (with LED cutout)|
|Brown: Tactile (no LED cutout) or linear (with LED cutout)|
- 5454_31 (SKCLAR and SKCMCQ)