Micro Switch SW and SN Series
Tentatively it appears that SW Series was the original Micro Switch keyboard series, introduced at the end of the 1960s. No early literature has been recovered, so the name “SW Series” remains conjecture at this time.
SW Series switches are open at the bottom. Companion series SN was provided to provide self-contained switches with a base to secure the internals. The charts provided by Honeywell show that SW and SN existed side by side from 1975 to 1999. It was previously suspected that SN replaced SW, but now it is clear that they served different purposes, and that it is more likely that SW Series was simply no longer advertised, having been superseded by SD Series in the mid 1970s.
No data exists on either series beyond 1999; Honeywell themselves report that all these switches were made obsolete in the 1990s.
SW Series switches are all open at the base: nothing holds the return spring inside the switch, and the Hall sensor is a slide-in fit. These switches clip into securing rails fitted onto the keyboard matrix PCB. The design rationale is not known, but a likely explanation is serviceability. Since the switches are contactless, they would typically only need servicing to replace a fouled housing or broken plunger. In such cases, there would be no need to supply or replace an expensive Hall sensor: all that is needed to replace a broken switch is to swap out the housing assembly, without the need for any desoldering. With that said, replacement switches do come with a fresh Hall sensor when purchased separately.
1SW Chart 1 lists a large number of models, but omits most product details. Known models are listed below.
The “R” suffix indicates a replacement switch sold separately in a box along with an instruction leaflet, return spring and two “spacers”, which presumably refer to the pry tools used to extract a switch that are enclosed in the box. The digits that follow the “R” are not explained; they could refer to switch weights in ounces, with 1.5 being a “half force” low-force switch (used together with a support switch on wide keys), 2 being semi-light weight and 8 being a heavy switch. (2 and 8 oz are weights also offered by SD Series; “half force” for SD Series was 1.3 oz.) These digits do not appear to be used by non-R modules, and non-R modules do not have a spring. (Presumably the choice of spring was covered by the bill of materials for the keyboard itself.)
The switches identified solely by a circled letter are models that were made obsolete during the series lifetime. The model number is obliterated and replaced with a chart revision letter. On the engineering charts, the obsoleted models are listed, but it is not always clear which entry corresponds to which model, as multiple models could have been made obsolete in the same revision.
|Catalogue listing||Action||Plunger colour||Plunger style||Source|
|1SW11-R||Momentary||Black||Sloped||eBay (date 7409)|
|Green||Sloped||1SW Chart 1|
|1SW11-R1.5||Momentary||Green||Sloped||1SW Chart 1|
|1SW12-R||Momentary||Green||Stepped||1SW Chart 1, eBay (date 7703)|
|1SW13-R||Alternate||Black||Sloped||1SW Chart 1, eBay (date 8121)|
|1SW15-R||Momentary||Black||Sloped||1SW Chart 1|
|1SW17-R||Momentary||Blue||Sloped||1SW Chart 1|
|1SW17-R1.5||Momentary||Blue||Sloped||1SW Chart 1|
|Ⓑ||Momentary||Blue||Sloped||1SW Chart 1|
|Ⓑ||Momentary||Blue||Sloped||1SW Chart 1|
|Ⓑ||Momentary||Blue||Stepped||1SW Chart 1|
|1SW17-R2||?||Blue||Sloped?||eBay (date 9541)|
|1SW17-R8||?||Blue||Sloped?||eBay (date 8444)|
|1SW19-R||Momentary||Blue||Sloped||1SW Chart 1|
|Ⓒ||Momentary||Black||Stepped||1SW Chart 1|
|Ⓓ||Momentary||Black||Sloped||1SW Chart 1|
|1SW31-R||Momentary||Green||Sloped||1SW Chart 1|
|1SW41-R||Momentary||Green||Sloped||1SW Chart 1|
|1SW43-R||Momentary||Red||Sloped||1SW Chart 1|
|1SW45-R||Momentary||Green||Sloped||1SW Chart 1|
|Ⓔ||Momentary||Red||Sloped||1SW Chart 1|
|1SW51-R||Momentary||Red||Sloped||1SW Chart 1, eBay (date 9511)|
|1SW51-R1.5||Momentary||Red||Sloped||1SW Chart 1|
|Ⓔ||Momentary||Red||Stepped||1SW Chart 1|
|1SW52-R||Momentary||Red||Stepped||eBay (date 8742)|
|1SW52-R8||Momentary||Red||Stepped||1SW Chart 1|
|1SW53-R||Alternate||Black||Sloped||1SW Chart 1|
|1SW54-R||Alternate||Black||Stepped||1SW Chart 1|
|1SW300-R||Momentary||Black||Stepped||1SW Chart 1|
|1SW301-R||Momentary||Black||Sloped||1SW Chart 1|
Leaflet PK 8503 2 shipped with replacement module 1SW51-R cites an additional plunger colour, of grey, which has a different internal design. The diagram in the leaflet is not clear enough to understand the difference; it is simply a guide to seating the return spring during switch replacement.
SN Series is documented by name, although so far only as a switch series. SN Series is the standalone equivalent to SW Series, which is either attached using dedicated clips, or is affixed to the PCB by adhesive pads prior to soldering. A base is fitted to the switch to contain the internal parts. The base notwithstanding, SN Series switches are externally identical to SW Series switches, and examination of a 201SN switch against a 1SW switch shows that the shells come from the same injection mould tooling.
1SW Chart 1 and 201SN Chart 1 were both drawn on the 11th of September 1995, and were both revised through to 1999. This means that for those years, the two series were directly related, offering different usage models: rail mount for SW and standalone mount for SN. The base for SN Series makes use of cutouts in the shell that provide clearance around the securing rails of SW Series keyboards. From this, it is not clear if SW and SN were conceived together, or whether SN was a later introduction to provide a standalone variant of SW, taking advantage of the cutouts in SW switches as a way to attach the base.
The base is noted in 201SN Chart 2 to be ultrasonically welded to the shell, which is why the switch cannot be opened for inspection and cleaning. The use of a welded (rather than clip-together) design might indicate that SN Series was created around SW Series to make use of the same tooling (without needing to retool to add a clip-together mechanism), but Cherry were themselves sealing M4/M5/M6 and M7 switches similarly, with no intention that they ever be opened for servicing, so a sealed shell could have been a specific design feature. One comment on the Deskthority forum noted that the move to clip-together shells was not done for servicing purposes, but to ease assembly, cutting out the time needed to glue or weld parts together; this comment has not yet been independently corroborated with any information provided by a manufacturer or in a publication.
Switches in SN Series fall into at least three sub-series:
|11SN Series||Snap-in panel mount||Illuminated and non-illuminated|
|101SN Series||Self-adhesive PCB mount||Non-illuminated|
|201SN Series||Illuminated, with optional lamp|
11SN illuminated and 201SN switches are centre-lit within a cylindrical plunger, and thus require special keycaps. Lamps were optional: there were separate part numbers based on whether or not a lamp was included.
Switches use either an SW packaged sensor unit (as widely observed in SW Series) or an SD sensor PCB, shared with SD Series. The types with packaged sensor units have two magnets, one on either side of the sensor. The types with a sensor PCB use taller magnets; the chart only shows the one magnet, but nonetheless indicate that two are present.
11SN switches have used both the old sequential numbering system as well as the later schematic numbering system. Just as with 1SW, some models were made obsolete within the lifetime of the series, and the model numbers were deleted from the charts.
|Catalogue listing||Action||Mount||Lamp||Force||Sensor||Circuit function||Notes|
|Ⓑ||Momentary||Snap-in||Not supplied||SD-10023||Sink pulse|
|11SN2A1||Alternate action||Snap-in||Not supplied||SW-11920|
|11SN2C1||Alternate action||Snap-in||Not supplied||SW-11921|
|11SN3D1||Indicator (sprung)||Snap-in||Not supplied||—||—|
|201SN1A1||Momentary||PCB||Not supplied||Sink level|
|201SN1B1||Momentary||PCB||Not supplied||SD-10023||Sink pulse|
|Ⓓ||Momentary||PCB||Not supplied||Sink pulse|
|Ⓑ||Momentary||PCB||Not supplied||Source level|
|201SN4A1||Momentary||PCB||Not supplied||Low force||Sink level|
|201SN4A2||Momentary||PCB||Supplied||Low force||Sink level|
|Ⓑ||Momentary||PCB||Not supplied||Low force||Sink pulse|
|Ⓑ||Momentary||PCB||Not supplied||Low force||Source level|
|Ⓑ||Momentary||PCB||Supplied||Low force||Source level|
|201SN5D1||Momentary||PCB||Not supplied||Low force||—||Dummy|
|Ⓑ||Momentary||PCB||Not supplied||Low force||Sink level|
|Ⓑ||Momentary||PCB||Supplied||Low force||Sink level|
|Ⓑ||Momentary||PCB||Not supplied||—||Indicator||Plunger permanently positioned in free position|
|Ⓑ||Momentary||PCB||Not supplied||—||Indicator||Plunger permanently positioned in alternate action actuated position|
|Ⓑ||Momentary||PCB||Not supplied||High force||Sink [sic]|
|Ⓒ||Alternate||PCB||Not supplied||Sink level|
|Ⓒ||Alternate||PCB||Not supplied||Source level|
At present there is no chart for 101SN.
Honeywell have kindly provided 1SW Chart 1 and 201SN Charts 1 (M) and 2 (A), which are freely available to all. 201SN Chart 2 (A) is an engineering chart and confidential details are redacted. At present, these are the only documents located. They are left in their original TIFF format for its sheer technical marvel of coming in so much smaller than the equivalent PNG and PDF.
- Micro Switch 1SW Series Chart 1, created 1995-09-11, last revised 1999-12-11
- Micro Switch 201SN Series Chart 1, created 1995-09-11, last revised 1999-04-14
- Micro Switch 201SN Series Chart 2 (A), created 1995-09-11, last revised 1996-08