Editing Futaba MR-6C series

{{Infobox dswitch
| image name        = BBC Micro Type 1 switch.jpg
| manufacturer      = [[Futaba]]
| switch type       = Linear
| contact mechanism = [[Metal leaf]]
| product code      = 
| family            = [[Futaba linear switch]]
| keycap mount      = Custom cruciform, bar
| switch mount      = [[Plate mount]]
| lifetime          = 
| force graph       = 
| actuation force   = Ca. 60 cN
| peak force        = 
| travel            = 3.1±0.5 mm
| bounce time       = 1 ms
}}

'''Futaba MR-6C series''' (formerly '''Futaba simplified linear''') is a series or sub-series in the [[Futaba linear switch]] family.

==Nomenclature==
ECPlaza depict the switch with two variants: cruciform mount, and bar mount.<ref name="ecplaza" /> This qualifies it to be considered a series, but it may be a sub-series. No datasheet has been found. The term "series" is used here to clarify that "MR-6C" represents more than a single switch configuration.

The provisional moniker arose from the reduced complexity of the switch over the visually very similar [[Futaba complicated linear]]. Despite being a simplified design, at nine components it is still more complicated than switches made today.

==Description==
Like most other Futaba linear switches, the shell is cylindrical with truncated sides, with a square top above the plate. It sits in a circular hole in the plate. The legs are threaded at the top and screw into place; the base plug of the shell is retained in place by the legs. One leg screws into a hole in the lower contact leaf; the slider presses both contact legs up against the other leg.

This switch is found in very few types of equipment; in most instances of it being identified, the actual switch used is [[Futaba MD series]] "complicated linear", which is visually distinct from MR-6C in terms of shape (colour should not be considered). Despite the cheapness of the simplified switch, it proved itself as a robust and durable product, standing up the wear and tear of the United Kingdom's schoolchildren in the 1980s. It was superseded in Acorn's range by the [[Futaba low-profile linear]] switch (in the Electron and Master 128), which was nowhere near as durable.

The switch has a non-uniform cruciform [[slider]] approximately 4.0 mm by 4.7 mm, with 1.2 mm wide arms, taking a 4 mm deep [[keycap]] stem. The distance between the plate and [[printed circuit board|PCB]] is 12.7 mm. Travel is around 3 mm.

==Specification==
The known specification, per ECPlaza,<ref name="ecplaza" /> is as follows:

{| class="wikitable"
|-
| Action || Momentary
|-
| Operating force || 100±25 gf
|-
| Travel || 3.1±0.5 mm
|-
| Pretravel || 0.8 mm or more
|-
| Overtravel || 0.5 mm or more
|-
| Life || 30M
|-
| Bounce time || 1 ms or less (new, and end of life)
|-
| Mounting pitch || 19 mm 
|}

Operating force at 100 gf is likely to be the terminal force, as otherwise it would be too high. This is consistent with all the first-generation switch specifications.

==Gallery==
The loose switches below were taken from a BBC Micro.

<gallery widths=250 heights=187>
File:Futaba simplified linear.jpg                                           | Futaba simplified linear switches
File:BBC Micro Type 1 switches close-up.jpg                                 | Switches mounted into a keyboard
File:BBC Micro Type 1 switches mounted.jpg                                  | Switches are plate mount
File:Futaba simplified linear -- base legs unscrew.jpg                      | Legs unscrew to permit removal of base plug
File:Futaba simplified linear -- base plug removed.jpg                      | Base plug removed from the switch
File:Futaba simplified linear -- contact leaves.jpg                         | Dual contact leaves (steel and copper), which press onto small lugs
File:Futaba simplified linear -- slider raises contact leaf against pin.jpg | Slider raises the two leaves up against one leg
File:Futaba simplified linear -- steel contact leaf removed.jpg             | Steel contact leaf removed
File:Futaba simplified linear -- copper leaf blocks slider removal.jpg      | Copper leaf prevents slider from coming out with damaging the leaf
File:Futaba simplified linear -- copper leaves are fragile.jpg              | Copper leaf is impossible to remove without damage
File:Futaba simplified linear -- slider disc.jpg                            | Spring recess in the slider contains a small black rubber disc
File:Futaba simplified linear -- shell exterior.jpg                         | Shell exterior
File:Futaba simplified linear -- shell interior.jpg                         | Shell interior
File:Futaba simplified linear -- components.jpg                             | All nine components
</gallery>

<small>One switch gave its life for this disassembly process.</small>

==Keyboards==
*[[ACC TDD]] (cruciform mount with complex stabiliser assemblies; 1985)
*[[Acorn Atom]] Issue 5 keyboard (cruciform mount)
*Many [[Acorn BBC Microcomputer]] keyboards (cruciform mount; 1982–1984)

==External links==
*Stairway to Hell Forums — [http://stardot.org.uk/forums/viewtopic.php?t=5138 Disecting a BBC Micro keyboard keyswitch] — including maintenance for weak contact leaves. Dated 2012-05-08. Retrieved 2015-07-27.

==References==
<references>
<ref name="ecplaza">ECPlaza — [http://www.ecplaza.net/eparts/product/10000059_10004405/mr-6c-various-switches.html MR-6C, Various Switches]</ref>
</references>

[[Category:Futaba switches]]
[[Category:Linear switches]]
[[Category:Metal contact switches]]
[[Category:List of all keyboard switches]]