Editing Futaba MD series

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{{Infobox dswitch
| image name        = Futaba complicated linear infobox.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          = 10M (KBM)
| force graph       = 
| peak force        = 3.5±0.8 oz (99±23 g) (KBM)
| pretravel         = 0.03±0.01&Prime; (0.8±0.25 mm) (KBM)
| travel            = 0.12±0.01&Prime; (3.0±0.25 mm) (KBM)
| bounce time       = 5 ms (KBM)
| patents           = [http://worldwide.espacenet.com/publicationDetails/biblio?CC=JP&NR=S5944725A&KC=A&FT=D JPS5944725A] (1982)
| inventor          = Hideo Chiyuushiya, Katsuki Shimizu, Masao Miyagishima, Shiyouhei Tanaka, Sadanori Okada, Riyouko Yamaguchi
}}

'''Futaba MD series''' (formerly '''Futaba complicated linear''') a provisional name for series in the [[Futaba linear switch]] family. The [[GRI]] equivalent series is '''KBM'''.

==Nomenclature==
The series name MD-4P is cited by Korean website ePartsHub, with a picture of Sandy's bar mount switch and the description "various switches".<ref name="epartshub" /> With MD-4PCS being a known part number, this would put both bar and cruciform mount in the same series. However, the cruciform mount, illuminated version is cited by a related website as "MD-7", suggesting MD-4P is the bar mount version, MD-4PCS is the cruciform mount version, and that "MD" is the common aspect of the part numbers.<ref name="ecplaza" /> Provisionally this is being used as the series name.

ePartsHub cite the switch as being made by Sejin. The only known PCB photograph of the Futaba [[Texas Instruments TI-99/4A]] keyboard bears both the Futaba and Sejin logos, but all cited instances of the product family (Futaba MD-4PCS, the [[Acorn BBC Microcomputer]] simplified linear switches, and the complicated linear switches in the [[Lear Siegler ADM 36]]) all cite simply Futaba as the source. While Sejin may have been the manufacturer, the series was clearly marketed by Futaba.

The previous "complicated" moniker arose due to the significantly greater complexity over the visually very similar [[Futaba simplified linear]].

==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. The legs are forced inside small holes in the contact plates, and in forcing the holes larger, the legs make a good connection with the contact plates.

The switch has been seen in black with a deep orange base plug, in white with an orange base plug, all black, and all white. The black version with the orange base cap has part number MD-4PCS.<ref name="MD-4PCS" />

The distance between the plate and [[printed circuit board|PCB]] is 12.7 mm.

The switch comprises 16 [[Parts per switch|parts]] in total, making it one of the most intricate switches ever designed (more so as it is only a linear switch):

*Shell
*Base plug
*Two threaded legs
*Return spring
*Leaf spring
*Contact assembly:
**Base
**Lower and upper contact leaves
**Plastic separator
**Rubber top
**Seal
*Slider:
**Main slider shaft
**Separate slider side (drops into the main shaft)
**Rubber ring
**Black dot

===Operation===
Two contact plates are placed around a plastic separator, inside a flat base. Above this is a thin flexible rubber sheet, which is sealed onto the sides of the base via an adhesive square. The leaf spring runs parallel to the slider, and it has a central tine with a nub that presses down on the rubber sheet. Via the rubber sheet, the pressure is transferred to the flexible legs of the movable contact, which touch the stationary contact.

The contacts have long exterior legs, with holes in them. The legs of the switch are of a greater diameter than these holes; when first screwed into the switch, they force a larger hole into the contact plates. As the metal is twisted inwards, it makes lateral contact against the sides of the legs.

==GRI KBM==
This switch was also sold by [[GRI]] as the KBM (keyboard switch, mechanical).<ref name="GRI-KBM" /> While GRI keyboards and keypads have been found with the standard "bumblebee" colour scheme, GRI also had bright white switches made with GRI branding.<ref name="HaaTa-GRI" />

KBM switches are described as having 3.5±0.8 oz operating force, which at just short of 100 g would make this the total force; assuming 35 g preload, then the actuation force would be around 67 g. Pretravel is given as 0.03±0.01&Prime; and total travel as 0.12±0.01&Prime;; this gives pretravel of 0.8 mm and total travel of 3 mm.

GRI's part numbers are:

;KBM-01-01
:Momentary
;KBM-01-01-AA
:Alternate action

==Specification==
The following table compares the specification provided by GRI with that reported to be found in FS-5104P4.<ref name="epartshub" />

{| class="wikitable"
|-
!Parameter!!Sejin!!GRI
|-
|Total force||100±25 gf||3.5±0.8 oz (99±23 g)
|-
|Total travel||3.1±0.5 mm||0.12±0.01&Prime; (3.0±0.25 mm)
|-
|Pretravel||0.8 mm or more||0.03±0.01&Prime; (0.8±0.25 mm)
|-
|Overtravel||0.5 mm or more||
|-
|Rated lifetime||10M||10M
|-
|Bounce time (max)||2 ms new, 5 ms at end of life||5 ms
|}

MD-4P series has a mounting pitch of 19 mm.

It's not known whether FS-5104P4 (Futaba-Sejin? Futaba Specification?) covers the alternate action switches.

==Variants==
===Cross mount===
The cross mount version 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. It has been seen in black with an orange base cap, white with an orange base cap, all black<ref name="EBAY-Altair" />, and all white.

The white/black/orange version has part number MD-4PCS. GRI KBM switches are also this variant.

The cross mount variant is keycap-compatible with the [[Futaba simplified linear]] switch.

The [[Futaba linear lock]] switch is the [[alternate action]] switch in this family.

===Bar mount===
All-black shell with a white slider<ref name="Sandy-bar_mount" />, white<ref name="eBay-PTC-45A" /> (base plug not visible), and black with an orange base and white slider.<ref name="GH-BP1210-D" /> One minor difference between the examples examined, is that the bar mount variant was found to have a transparent plastic cover over the contact assembly, instead of black rubber-like material.

This version may be model MD-4P.<ref name="ecplaza" />

===Multiple-switch return key===
TeleVideo keyboards (specifically TS-800A, TS-802 and TS-825) have been found with dual switches for the Return key. <ref name="GH-TeleVideo-8xx" /> These switches are white with a cream base plug, and otherwise appear to be identical to the white/orange switches used on the rest of the keyboard. The reason for having two switches side by side instead of a stabiliser is not known, nor why the switches are a different colour.

===Illuminated===
The illuminated version, with a crucform keystem, is given as MD-7;<ref name="ecplaza" /> it is not clear whether this is a series name or model number.

==Keyboards==

*Atari CX85 (ca. 1982) (black version)<ref name="Atari-CX85" /> <ref name="Atari-CX85-2" />
*GRI Model 771 Keyboard Subsystem (given as GRI KBM), as listed in [http://mattmik.com/downloads/viper/Volume1Issue09.pdf Viper magazine, 1979, volume 1, issue 9]
*GRI 9016 ASCII Series Keypad<ref name="GRI-KBM" />
*Later [[Krown Porta-printer]] keyboards (ivory with black base)
*Newbury 8000 series keyboard (white)<ref name="Newbury-8000" />
*Plantronics Vu Phone 3200
*TeleVideo Model 925 CRT Terminal keyboard (1981) (white version)<ref name="Televideo-925" />
*TeleVideo TS-800A satellite station keyboard (white with orange base, and white/cream for dual enter switch)<ref name="GH-TeleVideo-8xx" />
*TeleVideo TS-802 workstation keyboard (as above)<ref name="GH-TeleVideo-8xx" />
*TeleVideo TS-825 keyboard (unknown product) (as above)<ref name="GH-TeleVideo-8xx" />
*[[Televideo 910]]

===Other devices===

*PTC-45A machine keypad (white bar mount)<ref name="eBay-PTC-45A" />
*Canon Canola BP1210-D (black/orange bar mount)<ref name="GH-BP1210-D" />

==Gallery==
===Cross mount===
The following switches (part number MD-4PCS) are NOS from Electronic Surplus.

<gallery widths="250" heights="187">
File:Futaba complicated linear.jpg                                           | Futaba complicated linear switches
File:Futaba complicated linear legs.jpg                                      | The two legs are threaded and can be unscrewed
File:Futaba complicated linear base plug removed.jpg                         | The base plug is retained by the legs
File:Futaba complicated linear leg contact.jpg                               | The legs connect to the contact assembly via the bent edges of the holes
File:Futaba complicated linear contact assembly slides out.jpg               | The contact assembly slides out easily; note that the empty recess above the slider holds the latch track block in the [[Futaba linear lock]]
File:Futaba complicated linear main contact assembly removed.jpg             | Contact assembly removed from the switch
File:Futaba complicated linear contact assembly and leaf spring.jpg          | Contact assembly with leaf spring on top
File:Futaba complicated linear contact assembly separated.jpg                | Leaf spring and contact assembly
File:Futaba complicated linear contact assembly seal.jpg                     | The seal can be eased off safely with a sharp knife
File:Futaba complicated linear contact assembly opened.jpg                   | Contact assembly opened up
File:Futaba complicated linear contact assembly top plate removed.jpg        | Top contact plate removed, and the rubber sheet removed from the seal 
File:Futaba complicated linear contact assembly separator removed.jpg        | Separator plate removed, and top contact plate inverted to show the plating
File:Futaba complicated linear contact assembly bottom plate removed.jpg     | Bottom contact plate removed
File:Futaba complicated linear contact assembly base.jpg                     | Base seen from above and from below
File:Futaba complicated linear slider base.jpg                               | Base of the slider
File:Futaba complicated linear slider parts.jpg                              | Part of the slider is a separate piece that comes out separately
File:Futaba complicated linear slider ring.jpg                               | Slider side piece has rubber ring around connecting peg
File:Futaba complicated linear slider dot.jpg                                | The spring rests against a rubber circle of unknown function
File:Futaba complicated linear slider disassembled.jpg                       | Detailed views of the slider
File:Futaba complicated shell detail.jpg                                     | Shell detail, from below and above
File:Futaba complicated linear parts.jpg                                     | All sixteen components of the switch
</gallery>

<small>No switches were harmed by this disassembly process.</small>

===Bar mount===
The following switch was damaged during disassembly as it was not obvious that the pins had to be unscrewed.<ref name="Sandy-bar_mount" />

<gallery widths="250" heights="187">
File:Futaba complicated linear bar mount -- top view.jpg                     | Top view
File:Futaba complicated linear bar mount -- side view.jpg                    | Side view
File:Futaba complicated linear bar mount -- slider assembly detail.jpg       | Three-part slider
File:Futaba complicated linear bar mount -- three-part slider.jpg            | Slider parts
File:Futaba complicated linear bar mount -- transparent contact assembly.jpg | Transparent contact assembly
File:Futaba complicated linear bar mount -- contact assembly detail.jpg      | Contact assembly detail
File:Futaba complicated linear bar mount -- disassembled.jpg                 | Switch partially disasembled
</gallery>

==Specifications==

*[[:File:GRI KBM specification.pdf|GRI KBM specification]]

==References==
<references>
<ref name="ecplaza">ECPlaza — [http://www.ecplaza.net/eparts/3318325010/push-button-type-switches.html Push Button Type Switches]</ref>
<ref name="MD-4PCS">(Wayback Machine) Electronic Surplus — [http://web.archive.org/web/20120117015811/http://www.electronicsurplus.com/Item/150004/FUTABA%20-%20Switch_%20P_B_%20NO%20Keyboard_%20Package%20of%2020_%20-%20MD-4PCS/ MD-4PCS - Switch, P/B. NO Keyboard. Package of 20.] Archived 2012-01-17. Retrieved 2015-07-26.</ref>
<ref name="GRI-KBM">(Wayback Machine) GRI — [http://web.archive.org/web/20000818150348/http://www.grisk.com/keypad/9016.htm 9016 ASCII Series Keypad] Archived 2000-08-18. Retrieved 2015-07-26.</ref>
<ref name="HaaTa-GRI">Flickr — [http://www.flickr.com/photos/triplehaata/sets/72157635354802296/ GRI Model KBM 01 01] Retrieved 2015-07-26.</ref>
<ref name="EBAY-Altair">{{dead|eBay — [http://www.ebay.com/itm/190796348410 Altair George Risk Keyboard 2 756 013 A w 16 Pin Connector Used with My Merlin]}}</ref>
<ref name="Sandy-bar_mount">Sandy — [http://sandy55.fc2web.com/keyboard/futaba_old_complicate.html Futaba_complicated_Linear]</ref>
<ref name="GH-TeleVideo-8xx">Geekhack — [http://geekhack.org/index.php?topic=49503.0 Televideo Terminal Keyboard] Posted 2013-10-09. Retrieved 2015-07-26.</ref>
<ref name="Atari-CX85">Google+ — [https://plus.google.com/photos/113845661925823397356/albums/5598554335751689441 Atari CX85] Dated 2010-03-25. Retrieved 2015-07-26.</ref>
<ref name="Atari-CX85-2">Japanese keyboard blog — [http://kbd.rzw.jp/others/atari_cx85_futaba/ Atari CX85] (Japanese only) Dated 2013-10-20. Retrieved 2015-07-26.</ref>
<ref name="Newbury-8000">{{dead|eBay — [http://www.ebay.co.uk/itm/131148783988?orig_cvip{{=}}true Newbury 8000 series vintage computer keyboard. retro computing at its best]}}</ref>
<ref name="Televideo-925">Deskthority — [http://deskthority.net/photos-videos-f8/bunch-from-a-storage-unit-t4260.html Bunch from a storage unit]</ref>
<ref name="eBay-PTC-45A">eBay — [http://www.ebay.com/itm/251388448505 Machine Keyboard PTC 45A with Missing Key] {{volatile}} Retrieved 2015-07-26.</ref>
<ref name="GH-BP1210-D">Geekhack — [http://geekhack.org/index.php?topic=52346.0 What are theses switches?] Posted 2013-12-15. Retrieved 2015-07-26.</ref>
<ref name="epartshub">ePartsHub — [http://epartshub.com/sourcing/sourcing_PartsSrchList.jsp?type=K&StartClassCode=XEA0000000&cmpyCd=00001257&seriesCd=SR0002188&sType=D MD-4P]</ref>
</references>

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