Jump to page content

Micro Switch SW and SN Series

Contents

History

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they served different purposes, and that it is more likely that SW Series was simply no longer advertised, having been superseded by SD Series in the mid 1970s.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

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.

Models

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 Momentary Black Sloped? Flickr
1SW11-R Momentary Black Sloped eBay (date 7409)
Green Sloped 1SW Chart 1
1SW11-R1.5 Momentary Green Sloped 1SW Chart 1
1SW12-BL Momentary Black Sloped? Deskthority
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 Momentary Black Sloped? Flickr
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)
1SW18-R ? Blue Stepped eBay
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
1SW181-R Illuminated White ? eBay
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

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.

Subseries

Switches in SN Series fall into at least three sub-series:

Subseries Mount Type
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.

Models

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
11SN1 Momentary Snap-in SW-11921
11SN3 Alternate action Snap-in SW-11921
11SN15 Momentary Snap-in SW-11921
11SN17 Momentary Snap-in SD-10023 Sink pulse
11SN19 Momentary Snap-in SW-11921
11SN21 Momentary Snap-in SD-10575
11SN23 Alternate action Snap-in SW-11920
11SN31 Momentary Snap-in SD-10575
11SN33 Momentary Snap-in SW-11920
11SN33MR Momentary Snap-in SW-11920
Momentary Snap-in SW-12563
11SN51 Support Snap-in
11SN1A1 Momentary Snap-in Not supplied SD-10575
11SN1A2 Momentary Snap-in Supplied SD-10575
Momentary Snap-in Supplied SW-11920
Momentary Snap-in Supplied SW-12563
Momentary Snap-in Not supplied SW-12563
Momentary Snap-in Supplied SW-11920
Momentary Snap-in Not supplied SD-10023 Sink pulse
11SN1B2 Momentary Snap-in Supplied SD-10023 Sink pulse
11SN1C1 Momentary Snap-in Not supplied SW-11921
11SN1C2 Momentary Snap-in Supplied SW-11921
11SN2A1 Alternate action Snap-in Not supplied SW-11920
11SN2A2 Alternate action Snap-in Supplied SW-11920
11SN2C1 Alternate action Snap-in Not supplied SW-11921
11SN2C2 Alternate action Snap-in Supplied SW-11921
11SN3D1 Indicator (sprung) Snap-in Not supplied
11SN3D2 Indicator (sprung) Snap-in Supplied
201SN1A1 Momentary PCB Not supplied Sink level
201SN1A2 Momentary PCB Supplied Sink level
201SN1B1 Momentary PCB Not supplied SD-10023 Sink pulse
201SN1B2 Momentary PCB Supplied SD-10023 Sink pulse
Momentary PCB Not supplied Sink pulse
Momentary PCB Supplied Sink pulse
Momentary PCB Not supplied Source level
Momentary PCB Supplied Source level
201SN3D1 Momentary PCB Not supplied Indicator
201SN3D2 Momentary PCB Supplied Indicator
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
201SN5D2 Momentary PCB 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]
Momentary PCB Not supplied Scan
Alternate PCB Not supplied Sink level
Alternate PCB Supplied Sink level
Alternate PCB Not supplied Source level
Alternate PCB Supplied Source level

At present there is no chart for 101SN.

Documentation

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.

See also