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Alps series names and model numbers

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Series names

Part numbers for both keyboards and switches contain at least a portion of, and often all of the switch series name. The exact format of Alps series names remains a mystery, because so little documentation has been located. The series naming scheme has been altered at least once, and possibly more than once.

2-letter series

There is good evidence that SKCL and SKCM were called “CL series” and “CM series” (both in the 1994 catalogue and in the late 80s). So far, this example seems to be anomalous. No other two-letter series names have been found. Actual switch model numbers in both the 80s and 90s still took the form SKCLxx and SKCMxx, regardless of the short series names.

3-letter series

Switch series in the early 80s all had three-letter names; for keyboard types, this includes the following confirmed series:

The Alps Electric (USA) advertisement in Electronic Engineers Master 83–84 mentions “Series KFL Low Profile Keyboards” (confirming the existence of SKFL in 1983): this implies that “KFL” applies to both the keyboards and to the switches in them. (The only keyboard switches depicted in the advertisement appear to all be SKCC (momentary and alternate action), suggesting that SKFL pre-dated SKCL.)

These series names are found in Roland and Yamaha documentation (as switch model numbers) and as series names in Apple technical literature (sadly without any model numbers).

S-types

SCK series is a keyboard switch related to KBB/KCC/SKCC. This seemingly anomalous series name is not as unexpected as it would seem. The Roland MC-4 internal ten-key pad board (with KEH series switches) has assembly number KEH4A006, which is identical in format to SCH5A031, the original assembly number of the Alps AKB-3420 before it was revised to KCCAA902. That would put Alps KCC/KBB switches in SCH series, bringing it directly in line with SCK series (with H and K being notably close alphabetically). This muddies the already confusing KBB/KCC/SKCC quandary even further.

One consideration is that, as “K” seems to be associated with “tact” switches, “S” may have denoted linear types. It seems that this distinction was removed at some stage, with linear keyboard switches brought into the K family.

4-letter series

Alps converted from 7-digit models to 6-digit models, and extended switch series names to four letters, with an initial “S” added. For example, KHC10902 is reported to have changed to SKHCAB and thence to SKHCBEA010.

The same applied to CL and CM series; Information that seemingly arrived via Sandy indicates that in the 1994 catalogue, CM and CL series were found alongside SKFR and SKFS series, but by the late 90s, this was changed to “SKCL/SKCMシリーズ” (“SKCL/SKCM series”) in the datasheet for SKCLCQ and SKCLAR.

The Technology Transplant switch kit for the Roland TR-909 referred to KFL switches as “SKFL”, suggesting that KFL was itself changed to SKFL.

Keyboard switch series with confirmed or tentatively confirmed four-letter names include:

So far, it is not known how many series were renamed: some may have been end-of-life at the point that the new names were introduced, or in extended lifetime only (manufactured but no longer advertised), and Alps may not have retrospectively renamed them.

The following keyboard switch series have confirmed new-style part numbers, but no literature has been found giving series names:

Series families

Based on Alps EUROPEAN SELECTION 2000/2001, switch series names are generally four letters long, beginning with S, with the following families:

Family Type
SS__ Slide switches
SP__ Push switches
SR__ Rotary switches
SK__ “Tact Switches” (formerly including keyboard switches)

Within SK__ family, there are these subfamilies (descriptions in quotation marks are verbatim from Alps literature):

Family Type Notes
SKC_ Keyboard switches with “switchplates” (SKCC, SKCL/SKCM and SKCP)
SKE_ Elastic contact switches — “Tact Switches”: “Metal Contact with LED” (SKEC), “Tact Switches”: “Elastic Contact (Standard Bulk Type)” (SKEY) SKEC as a metal contact switch cannot be verified at present, as it appears to be an obsolete type, and thus there are no online specifications for it; other SKE* types all appear to be elastic contact
SKF_ Keyboard switches with plain metal contacts (thus far, SKFL, SKFM/SKFN and SKFR/SKFS)
SKH_ “Tact Switches”: “Metal Contact (Standard Bulk Type)”, “Metal Contact with LED” (SKHQ, SKHJ), “Mechanical Contact (SMD Type)”
SKP_ “Tact Switches”: “Elastic Contact (Standard Bulk Type)”, “Metal Contact/Soft feeling Type” (SKPL) SKPL is given as “metal contact” in the European catalogue, but the product specification given under the SKPL Series product information clearly shows that it has a dome inside.
SKQ_ “Tact Switches”: “Metal Contact (Standard Bulk Type)” (SKQE, SKQN), “Multifunction Tact Switch” (SKQU), “Mechanical Contact (SMD Type)” (SKQY), “Metal Contact” (SKQR)
SKR_ “Tact Switches”: “Elastic Contact (with LED)”

Switches

Alps push button model numbers are so far found to typically follow one of two patterns. There is no known cut-over point. This is not unprecedented, as SMK part numbers changed in a similar manner.

Older pattern

The older pattern is not fully understood, and the format is schematic but codes are seemingly specific to families of switch series.

Roland documentation offers a couple of KFL part numbers; sadly no other machines with KFL switches have available service manuals or switch details in these manuals.

The table below includes non-keyboard types, as source data for pattern interpretation.

Part Series Type Source
KFL10903 KFL Momentary Roland SBX-80 and TR-090 service notes
KFL11904 KFL Momentary illuminated Roland SBX-80 and TR-090 service notes
KED10001 KED Momentary, with 2-unit relegendable keycap Roland TR-808 service notes
KED10903 KED Momentary, with 1-unit relegendable keycap Roland TR-808 service notes
KEH10903 KEH Momentary Roland MC-4 service notes
KHH10908 KHH Momentary (non-keyboard) Yamaha QX3 service manual
KHJ10902 KHJ Momentary (non-keyboard) Roland SBX-80 service notes
KHJ11901 KHJ Momentary illuminated (non-keyboard) Roland SBX-80 service notes
SCK41167 SCK Momentary, with 1-unit relegendable keycap Roland CSQ-100 and CSQ-600 service notes
SCK41168 SCK Momentary, with 2-unit relegendable keycap Roland CSQ-100 and CSQ-600 service notes

These codes are schematic, but the positions of the digits is not yet clear. The general pattern is as follows:

Kxyabcdd

The positions have the following interpretations in Kxx types (SCK follows a totally different pattern):

x
Thus far, this seems to indicate contact classification (see under newer pattern, below).
y
Series indicator within the above classification (again, see newer pattern, below)
a
This is always a 1 in discovered examples; this column was deleted in the newer scheme.
b
Inner subseries: 0 = normal (replaced with “A”), 1 = LED illuminated (replaced with “F”), 2 = incandescent illuminated, 5 = vertical (replaced with “L”)
c
This is either 0 or 9 in discovered examples; generally 9 is the default value, with 0 being the first alternative variation (e.g. 2-unit versus 1-unit keycap). This position is not well understood.
dd
Generally this is the sequence number within the series or subseries. For standard keyboard switches, 3 is a common value, for a reason yet to become clear. Only one example has been found greater than 09, namely KEC10010, and so far it is impossible to understand the details of KEC from the only photo available.

Subseries

There are at least two subseries patterns.

Outer subseries groupings combine multiple series together. For example, standard-size tact switches were divided as follows, according to the switch operation:

Inner subseries used the second digit for the grouping. This led to terms such as “KEF10 Joint Series”, which the non-illuminated KEF series (KEF10) variants with a “joint stem”, i.e. with a keystem instead of a flat slider. In some cases it seems like the codes are split even/odd by keystem, but presently insufficient information is available to be certain.

Newer pattern

Newer pattern model numbers take the form:

SKxyza

The positions have the following interepretations:

x
Thus far, this seems to indicate contact classification when it comes to keyboard switches; see series families above.
y
Series indicator within the above classification, such as “B”, “C”, “L”, “M” and “P” within SKCy; these are often paired, with the linear type having the lower of two adjacent letters (SKCL/SKCM, SKFM/SKFN, and SKFR/SKFS)
z
Subseries, covering a particular set of characteristics (see below)
a
Individual switch model letter; this last character remains a complete mystery. In some subseries, it starts at “A” (such as SKFSAA or SKFNAA) while with other subseries the earliest character is at least a few letters in (as with SKFRAC, the lowest known SKFR model, and SKCLJC, the lowest SKCLJa type, and it’s never clear whether all subtypes started at A or whether some subseries skipped the first few letters).

“SK” is reported to stand for “single key switch” according to Sandy, per the 1994 catalogue. This may not be a literal meaning, but rather it might be a convenient interpretation for English-speaking customers.

Subseries

In this schema, with keyboard, outer subseries were used for linear versus tactile: SKCL/SKCM, SKFM/SKFN and SKFR/SKFS, with linear coming first in each pair.

Other characteristics use inner subseries. It seems that some subseries letters (in particular F) are shared between more than one series. The explanations given below relate to this schema as it applies to keyboard switches, but some application to other pushbutton switch types is also noted for clarity.

Subseries Example meanings
A The initial design variant of the switch is denoted “A”. In all keyboard switch examples to date, “A” covers single-pole, single-throw normally-open momentary switches. In SKCC series, it appears to indicate switches with a tall slider.
B “B” denotes the first alternative design variant (e.g. through hole versus surface mount). In SKCM series, it appears to denote damped (SKCMBB: SKCM Cream Damped), while in SKCC series, it appears to denote standard slider height.
C The only known example in keyboard switches is SKCMCQ, which seems to be a replacement model number for white Alps (SKCMAQ); it seemed like “C” might denote bamboo switches, but as SKCM Green model SKCMAT seems to be bamboo, the meaning of “C” and the difference between SKCMCQ and SKCMAQ remains a mystery.
F In all examples to date, this indicates an illuminated switch. This is SKCLFQ (SKCL Yellow with red LED) and SKCLFM (SKCL Yellow with green LED) from SKCL series, and SKFRFA (red LED), SKFRFB (green LED) and SKFRFC (amber LED) from SKFR series. Non-keyboard series such as SKEC also follow this pattern.
J Alternate action (SKCLJC: grey Alps Lock)
K Double action (SKCLKB)

Additional letters found in non-keyboard series include:

Subseries Example meanings
G Tentatively, G is to F, what B is to A: an alternate form factor of illuminated switch.
L This seems to denote a vertically-orientated switch.

Other letters are known from non-keyboard switches, but additional research would be required to identify patterns.

Part numbers

The next pattern comprised the model number plus the part number suffix. The part number suffix was generally four characters, typically three digits followed by a letter (e.g. 001A) or four digits (e.g. 0001). All the following examples are taken from official Alps or Forward Electronics switch packaging, with the years given where known:

Model Part
SKCCAF SKCCAF002A (1987)
SKCCBJ SKCCBJ0001
SKCCBK SKCCBK0001
SKFRAC SKFRAC000A (1999)
SKFSAA SKFSAA000A (2004)
SKPAAA SKPAAA000A (200?)

This has been replaced since with a unified part number format with the three digits and single letter reversed, e.g. “SKECADA010”.

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