Cherry M4/M5/M6 part number schema
The following page provides a reconstruction where possible of the Cherry M4/M5/M6 part number schema. See also the Serie M7 schema.
See also M4/M5/M6 variants for known switch models and M4/M5/M6 examples for keyboard examples found to date.
Contents
Overview
It appears that no formal schema existed, and that part numbers were simply assigned sequentially in most cases. For example, 10° stem can be denoted by +10 (as with all the types in the 1973 catalogue, such as M61-0100 and M61-0110) and by +1 (as with M41-0126 and M41-0127). The one known tactile type has non-descript part number M51-0229. However, there are a number of commonalities.
It appears that the T stem was not introduced until later; no mention was made of stem shape in the 1973 and 1974 catalogues, while in 1979 multiple stem shapes exist. The drawing for Burroughs M51-0131—formerly M51-0139—shows a T stem and dates back to 1973, but with nine or ten documented revisions and a Style B shell depicted by the end of the revisions, one cannot be sure what the original looked like. It is not keycap-compatible with normal 12 mm keystems, and it is not clear what led to the introduction of T stems from Alps and Cherry by the end of the 80s. What we do know from the 1985 EEM advertisement is that M61-0120 (0° T) replaced M61-0100 (0° straight).
It is possible that the huge rise in configuration options led to an explosion of non-standard part numbers; that is, it was not possible to define a schema for options not conceived when the series was introduced. (Later options included two extra illumination methods and multiple keystem designs.)
Note however that Style A, AB and B switches with T stems are limited to single pole momentary configuration. The corbel for the T vane of the keystem runs right down inside the slider, and does not leave room for the second pair of contacts (the sliders can only operate one set of contacts). Based on patent drawings, such switches do not leave room for the alternate action mechanism either, which is why B70-05AB has T switches for momentary keys and bar (straight) switches for the lock keys.
By comparison, the style C and D slider from the German Serie M7 switches is significantly slimmer and supports dual contacts in addition to T and cruciform keystems.
Part number format
Part numbers follow this form:
MSC-0TAB
The positions are as follows:
| Position | Code | Suggested meaning |
|---|---|---|
| 1 | M | M: keymodule |
| 2 | S | Subseries (4, 5, 6, 7); no values below 4 are known to exist, and 8 and above were used for entirely new switch series |
| 3 | C | The number of contact pairs; this has only been seen as 1 or 2 |
| 4 | 0 | This is always zero in known types |
| 5 | T | Nominally this indicates the switch type; see the subtypes table below for details. |
| 6 | A | Undefined |
| 7 | B | Undefined |
Subseries
M4 is the illuminated type. M5 and M6 are not clearly separated. The following table describes the known switch characteristics within each subseries according to the catalogue listings.
M7 is not part of this series, but it was advertised in the US, presumably due to the need for centre illumination that was not offered by M4.
| Subseries | Stem | Force | Angle | Contacts | Action | Illumination |
|---|---|---|---|---|---|---|
| M4 | Straight, round | Various | 0° and 10° | 1A, 2A? | Momentary and alternate | Corner |
| M5 | Straight, T | Various | 0° and 10° | 1A, 2A | Momentary | None |
| M6 | Straight, T | Various | 0° and 10° | 1A, 2A, 1A+1B | Momentary and alternate | None |
M42 is not proven to exist, but NSN 5930-01-102-5338 is said to represent Cherry part M42-0101. This NSN only appears on two sites, and the Cherry part number only appears on one; neither site has any accompanying information about the part aside from it being a Cherry push switch.
Subtypes
The following table lists suggested subtypes based on the catalogue listings.
| Subtype | Usage in 1973–74 | Usage in 1979–82 |
|---|---|---|
| 0 | Unused | Various switches; this includes the mechanical shift lock assembly switches formerly in subtypes 3 and 5 |
| 1 | Standard switches | Various switches |
| 2 | Unused | A handful of assorted switches: the one tactile type, two of the space bar types, and one of the 6 oz switches |
| 3 | Used for the shift switch in a mechanical shift lock assembly | Unused |
| 4 | Unused | |
| 5 | Used for the shift lock switch in a mechanical shift lock assembly | Unused |
| 6 | Unused | |
| 7 | Unused | |
| 8 | Alternate action | |
| 9 | Only found in the part number of the only 1A+1B switch (from 1974) | |