Editing Four-tab clone

'''Four-tab clone''' refers to a shell design that is common to a wide variety of [[Alps clone]] switches.

==Description==
The majority of such switches are not branded; the only external clue as to the switch type is the [[mould numbering]] on the upper shell. The shells all follow a standard pattern, and with the mould numbering and branding removed, they would be virtually indistinguishable. The originator of this design is not known.

The lack of branding on early generations of Alps switches has led to four-tab clones being widely mistaken for genuine [[Alps SKCL/SKCM series]] and [[Alps SKBL/SKBM series|SKBL/SKBM series]] switches. The defining characteristic of a four-tab clone is that the shell is supported by the mounting plate from below by four small tabs; Alps themselves used two long tabs. No Alps Electric switches used the four small tabs, but some Alps clones did use long side tabs.

<div style="text-align: center">
<gallery widths="150">
File:Switch recognition--Alps--Original.svg       | '''Two long tabs:'''<br>typically genuine Alps
File:Switch recognition--Alps--Four tab clone.svg | '''Four small tabs:'''<br>a four-tab clone
</gallery>
</div>

Four-tab clones may be referred to as '''Simplified Alps Type II''' or '''XM'''. The former is an obsolete term with an unclear meaning, which is best avoided. The latter is a misconception that all four-tab clones are from the same manufacturer, of previously unknown name; "XM" stands for [[Xiang Min]] and thus the only switches legitimately referred to as "XM" are those manufactured by Xiang Min. '''Simplified Alps Type IV''' describes a specific switch, [[alps.tw Type OA2]].

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==Examples==
Families of four-tab clones include:

===Unbranded===
*[[Xiang Min KSB series]]
*[[Xiang Min KSBF series]]
*[[Taiwan Tai-Hao APC series]] (current)
*[[Hua-Jie AK series]]
*[[Hua-Jie AKF series]]
*[[Simplified Alps Type IV]]

===Branded===
*[[ATW Alps clone]]
*[[Taiwan Tai-Hao APC series]] (older)
*[[SFON Alps clone]]
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==Counterexamples==
The following non-Alps switches do have the two long side tabs:

*[[Simplified Alps Type III]]
*[[GA Alps clone]]
*[[alps.tw Type OD3]]

The following switches have incompatible leg spacing and are not compatible with Alps PCBs:

*[[YH-B switch]]
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==Uncertain==
The following switches have yet to be inspected in detail:

*[[Kwanda PB11C05]]
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==Recognition==
===Mould numbering===
Mould numbering examination is a first step that allows for the recognition of certain switches. In particular, NW:A## numbering appears to always indicate Taiwan Tai-Hao APC series switches. N:A## and N:## typically indicates Xiang Min's non-LED switches.

<gallery widths=250 heights=187>
File:Four-tab clone -- APC.jpg                       | NW:A## — [[Taiwan Tai-Hao APC series]]
File:Four-tab clone -- Xiang Min (AN).jpg            | N:A## — [[Xiang Min KSB series]]
File:Filco Zero KSB-C switches showing numbering.jpg | N:## — [[Xiang Min KSB series]]
</gallery>

Identification of specific switches requires that the switch be opened and the internals examined; care should be taken as the contacts are fragile and supported chiefly by the upper shell, and Alps clone switches are very difficult to reassemble while still soldered into the keyboard.

===Internals===
alps.tw classification is by switch internals. Some of the details are quite subtle, for example how much separation there is between the fingers of two-finger switches.

{| class="wikitable"
! Movable contact !! Stationary contact !! Leaf !! Mould numbering !! Designations
|-
| [[File:Alps.tw Type OA2 -- movable contact.svg]]
| Large
| Wide steel
| Alps
| [[alps.tw Type OA1]]
|-
| [[File:Alps.tw Type OA2 -- movable contact.svg]]
| [[File:Alps.tw Type OA2 (A) -- stationary contact.svg]]
| [[File:Alps.tw Type OA2 (A) -- click leaf.svg]]
| S:#A##
| [[alps.tw Type OA2]] variant A<br>(Simplified Alps Type IV)
|-
| [[File:Alps.tw Type OA2 -- movable contact.svg]]
| Large
| [[File:Alps.tw Type OA2 (B) -- click leaf.svg]]
| S:##
| [[alps.tw Type OA2]] variant B
|-
| [[File:Alps.tw Type OA2 -- movable contact.svg]]
| Large
| Wide steel
| Unnumbered Alps
| [[Simplified Alps Type III]]
|-
| One finger
| [[File:Alps.tw Type OA3 -- stationary contact.svg]]
| Wide steel
| NW:A##
| alps.tw Type OA3:<br>[[Tai-Hao APC series]] (older)
|-
| One finger
| [[File:Alps.tw Type T2 -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| NW:A##
| alps.tw Type T2:<br>[[Tai-Hao APC series]] (newer)
|-
| [[File:Alps.tw Type T4 -- movable contact.svg]]
| Large
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| S:#A##
| [[alps.tw Type T4]]
|-
| [[File:Alps.tw Type OA4 -- movable contact.svg]]
| [[File:Alps.tw Type OA4 -- stationary contact.svg]]
| [[File:Alps.tw Type OA4 -- click leaf.svg]]
| S:##<br>S:#A#
| [[alps.tw Type OA4]]
|-
| [[File:Alps.tw Type OA4 -- movable contact.svg]]
| [[File:Alps.tw Type OA4 -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| Unknown
| [[Hua-Jie AK-CN2]]
|-
| [[File:Alps.tw Type T1 -- movable contact.svg]]
| [[File:Alps.tw Type OA4 -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| S:##<br>NW:#,SE:#<br>S:#A##
| [[alps.tw Type T1]]
|-
| [[File:Xiang Min KSB-LE -- movable contact.svg]]
| [[File:Alps.tw Type OA4 -- stationary contact.svg]]
| [[File:Alps clone internals -- LED recess.svg]]
| SW:#
| [[Xiang Min KSB-LE]]
|-
| [[File:Alps.tw Type T1 -- movable contact.svg]]
| [[File:Alps.tw Type OA4 -- stationary contact.svg]]
| [[File:Alps clone internals -- green LED.svg]]
| S:##
| [[USw LABG01]]
|-
| [[File:USw LABI01 -- movable contact.svg]]
| [[File:Xiang Min KSB -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]] <!-- approximate! -->
| NW:##,SE:##
| [[USw LABI01]]
|-
| [[File:Hua-Jie AK-xN2 (2) -- movable contact.svg]]
| [[File:Hua-Jie AK-xN2 (2) -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| NE:#,SW:#
| [[Hua-Jie AK-CN2 (2)]]
|-
| [[File:Hua-Jie AK-xN2 (2) -- movable contact.svg]]
| [[File:Hua-Jie AK-xN2 (2) -- stationary contact.svg]]
| None
| NE:#,SW:#
| [[Hua-Jie AK-DN2 (2)]]
|-
| [[File:Xiang Min KSB-C+N -- movable contact, curved crossbar.svg]]
| [[File:Xiang Min KSB -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| N:A##<br>N:##
| [[Xiang Min KSB-C]]<br>(alps.tw Type T3)
|-
| [[File:Xiang Min KSB-C+N -- movable contact, curved crossbar.svg]]
| [[File:Xiang Min KSB -- stationary contact.svg]]
| None
| N:A##<br>N:##
| [[Xiang Min KSB-N]]
|-
| ?
| ?
| ?
| None
| [[YH Alps clone]]
|-
| Two finger skinny taper
| Small flat metal
| Silver narrow leaf
| None
| [[YH-B Alps clone]]
|-
| [[File:Alps.tw Type T8 -- movable contact.svg]]
| [[File:Alps.tw Type T8 -- stationary contact.svg]]
| [[File:Alps clone internals -- generic PBS leaf.svg]]
| S:#A##<br>S:A##
| [[alps.tw Type T8]]
|-
| ?
| ?
| ?
| N:{Kwanda logo}-A
| [[Kwanda PB11C05]]
|}

==Incompatible leg spacing==
At least one switch has legs spaced further apart than those of Alps switches and clones. The [[YH-B switch]] was sold as a replacement part for certain Guitar Hero controllers. It was previously referred to as the "YH-B Alps clone" before it became apparent that it is built to a revised physical specification. The images below show comparable "CS" and "YH-B" parts, very similar internally and externally, but with standard and incompatible leg spacing respectively.

<gallery widths=250 heights=187>
File:Four-tab types 1.jpg | Top; the switches are orientated 180° apart
File:Four-tab types 2.jpg | Tops
File:Four-tab types 3.jpg | Bottoms
File:Four-tab types 4.jpg | Comparison with [[Alps SKCM Green]]
</gallery>

The third leg in these switches appears to be present only for physical support; it is not electrically connected to anything, and can be removed if not required. The CS type can be purchased with either two or three legs.

[[Category:Designations]]