Editing Hi-Tek Series 725

{{TODO rethink|reason=Colour tables are obsolete; colour table needs converting to variants table and the remainder of the page needs restructuring into a less disjointed arrangement}}

{{infobox dswitch
| image name        = NMB Hi-Tek white.jpeg
| manufacturer      = [[Hi-Tek]]
| contact mechanism = [[Contact mechanism#Metal leaf|Metal leaf]]
| switch type       = Clicky; tactile; linear; latching
| peak force        = 
| introduced        = 1983
| discontinued      = 1995 or later
| patents           = [http://www.google.com/patents/EP0124206A1 EP0124206] (1984)
}}

'''Hi-Tek Series 725''' was [[Hi-Tek Corporation]]'s [[DIN-compliant]] keyboard series, introduced in 1983; the name refers to how these keyboards are a maximum of 0.725&Prime; from the desk surface.<ref>Deskthority — [https://deskthority.net/keyboards-f2/hi-tek-corp-history-t10435.html Hi-Tek Corp. History]</ref> "Series 725" also refers to the switches used in these keyboards.

==Series 725 keyboards==
{{Main|Hi-Tek Series 725 keyboards}}

Series 725 was introduced by Hi-Tek shortly before their acquisition by Minebea. The name does not refer to any particular size or shape of keyboard, but rather to the reduction in desk-to-keycap height that was made possible by the use of compact switches.

See:

*[[Hi-Tek Series 725 first generation]]: typically Model F clone layout
*[[Hi-Tek Series 725 second generation]]: typically Model F clone layout
*[[NMB RT-100/RT-8200 series]]: full-size keyboards; later variants gained [[Windows key]]s

==Series 725 switches==
[[File:Space-invader.png|thumb|A space invader that the switches are named for]]

Series 725 is a family of [[metal contact]] switches designed by [[Hi-Tek Corporation]] in the early 1980s, and patented post-introduction in 1984. These switches are used primarily, if not solely, in keyboards manufactured by Hi-Tek and [[NMB]]. Series 725 switches are commonly known as '''space invader''' switches, due to their resemblance to the enemy characters in Taito Corporation's ''Space Invaders'' game from the late 1970s. The Chinese name for them is "怒熊", translating to '''Fury Bear''' or '''Angry Bear'''. The series was also referred to as '''NMB Hi-Tek''' when the relationship between Hi-Tek and NMB was not known. 

Series 725 switches are notable for having a particularly unusual [[keycap mount]] — the [[slider]] is large and flat-topped and the [[keycap]] clips over the top. The [[return spring]] reaches to the top of the slider, meaning that the keycap sits over and around the slider, reducing the height requirement of the keyboard significantly while retaining full travel (the switches are specifically patented as "low profile"). As a result, there is no upper shell, as the slider also serves this purpose.

Like the previous [[Hi-Tek High Profile]] switches, the slider contains a horizontal plastic bar that holds apart a pair of vertical electrical contacts, which close together when the slider is depressed or removed from the switch. Each contact has two legs, for a total of four arranged in a square.

The early switches had a rounded slider with a large opening at the top; this "soap dispenser" or "Gundam" design is the one featured in Hi-Tek's patent. The Series 725 keyboards featuring these switches lack the NMB branding on the PCB, and do not appear to have a manufacturing date on the PCB either.<ref>geekhack — [http://geekhack.org/index.php?topic=33130.msg1450817#msg1450817 What did you get in the mail today?]</ref> The age of the keyboard can be estimated by the lack of dedicated LED switches.<ref>geekhack — [http://geekhack.org/index.php?topic=60707.msg1499485#msg1499485 NMB Hi-Tek Space Invaders discussion topic]</ref>

Within a couple of years of their introduction, the more familiar "space invader" design was introduced, that was maintained for the rest of the switch family's production lifetime; the opening in the slider was reduced in size and made rectangular. The "eyes" in the slider help to visually determine the switch variation where the same colour has been used for more than one switch type.

As with the earlier Hi-Tek switches, the return spring has a tight cluster of turns in the centre as well as at each end.

Keyboards with Series 725 switches typically use a different switch for the space bar. The only difference is that the spring is longer, resulting in a stiffer switch.<ref name="HaaTa1">geekhack — [http://geekhack.org/index.php?topic=12861.0 Nmb rt-8251t]</ref>

Series 725 switches also use custom [[stabiliser]]s where the custom-shaped stabiliser wire clips directly under the switch shell.<ref name="RT101-3">Deskthority — [http://deskthority.net/photos-videos-f8/nmb-rt101-t4076.html NMB RT101+]</ref> There are at least two shapes of switch shell depending on whether a stabiliser is required, but the stabiliser version is used indiscriminately, probably to ease stock management. Reinsertion of a stabiliser wire can require de-soldering a switch.

Series 725 switches were introduced at least as early as 1985.<ref>Deskthority — [http://deskthority.net/keyboards-f2/picked-up-an-xt-keyboard-the-other-day-t3909.html Picked up an XT keyboard the other day]</ref> The NMB RT8255+ with Windows keys indicates that they were produced until 1995.

==Variations==
===Linear===
White slider, with one or two eyes, beige slider (two eyes), or grey slider (one eye). Space bar can be white or neon green.<ref>geekhack — [http://geekhack.org/index.php?topic=4757.msg68398#msg68398 Weird keyboard is here.]</ref> The LED variant has a magenta slider.

Two-eye white sliders have the click track from a click switch, but the click arm is simply omitted in linear keyboards.

===Tactile===
Grey slider (two eyes), beige slider (one eye), and black slider (two eyes). Space bar likely to use a neon green slider, which will be linear — tactile keyboards appear to all use linear space bar switches. The LED variant has a pink slider.

In tactile variants, tactility is provided by the contact leaves. On a tactile variant, the contact leaves have a single extra kink on each arm. As the slider bar is depressed, it moves through these extra kinks before allowing the contacts to touch. This extra resistance from the additional kinks provides tactility on the down-stroke and upstroke, with the upstroke being slightly more pronounced. The contact separator bar within the slider is also narrower, to fit within the reduced spacing between the contacts.

Some tactile keyboards use pink switches under the [[lock key]]s; notwithstanding the different colour and slider planform, the difference with these switches is not known.

===Clicky===
Black slider, or white slider (two eyes), and white, black, cyan or blue or brown for the space bar. While tactile keyboards appear to all use linear switches, clicky keyboards use clicky switches for space bar.

The click is achieved by way of a plastic follower arm that runs inside an external groove at the rear of the slider.<ref>YouTube — [http://www.youtube.com/watch?v=sUqYADAkwhE NMB Hi-Tek Trailing arm click]</ref> This follower arm is plainly visible and accessible without needing to dismantle the switch. This arm also provides the tactility, so the kinks in the contact leaves used in the tactile switches are unnecessary in clicky switches, and are omitted.

===Latching action===
The latching variant is black with an eye in the dead centre (instead of the usual N or NE/NW positions). The slider contains a latch track, and the latch arm is connected to the switch shell and faces upwards into the track.<ref name="laugh" />

===Integrated LED===
There are both tactile (pink) and linear (magenta) versions with integrated LED support. Unlike most switches, these have two LED holes, at the NE and NW corners. The corresponding slider corners are tapered away, with the keycap mounting recess moved to the N position.

==Colours==
{| class="switch-recognition-table"
{{switch colour multi | white   | White       | Linear (one<ref name="DT-white-linear" /> or two<ref name="Sandy-N-97-KANA" /><ref name="Sandy-RT101-WL" /> eyes) | Clicky (two eyes)<ref name="gh-RT101-white-click" />; white switches used for space bar will have a longer spring to increase resistance<ref name="P2812" /> with the space bar slider marked with a dot<ref name="gh-RT101-white-click" /> | Clicky, with tapered planform and LED holes<ref name="Sandy-RT101">Sandy — [http://sandy55.fc2web.com/keyboard/rt-101.html RT-101+]</ref> }}
{{switch colour multi | #F7EE00 | Yellow      | Linear; reported to be slightly lighter weight than white<ref name="laugh" /> }}
{{switch colour multi | #A0A0A0 | Grey        | Tactile (two eyes) | Linear (one eye)<ref name="Sym2" /> | Linear (two eyes) |}}
{{switch colour multi | #DEB595 | Beige       | Linear (two eyes)<ref name="Commodore" /> | Tactile (one eye) <ref name="rzwv-sliders" /> | Clicky (presumably); used for space bar switch with powder blue switches<ref name="Sandy-RT101" /> }}
{{switch colour multi | #CAF432 | Neon green  | Linear; used for space bars on linear and tactile boards }}
{{switch colour multi | #00CAC4 | Sea green   | Appears to be linear; purpose unknown, probably another space bar switch<ref name="AE-SG">AliExpress — [http://www.aliexpress.com/store/product/7pcs-Bag-HITEK-Keyboard-switch-green-and-fluorescence/1059110_32651117995.html Buy 7pcs/ Bag HITEK Keyboard switch green and fluorescence …]</ref> }}
{{switch colour multi | black   | Black       | Clicky (two eyes; 45 g tactile force, 85 g terminal force<ref name="KBDMania-Memorex" />) | Tactile (two eyes)<ref name="laugh" /> | Latching action (centre eye)<ref name="laugh" /> }}
{{switch colour multi | #DAF2FE | Powder blue | Clicky<ref name="Sandy-RT101" /> }}
{{switch colour multi | #83D2FD | Cyan        | Clicky; for space bars on clicky boards, and has a longer spring to increase resistance }}
{{switch colour multi | #40A0F4 | Blue        | Variant of the above }}
{{switch colour multi | #A97B59 | Brown       | Variant of the above (85 g tactile force, 100 g terminal force<ref name="KBDMania-Memorex" />) }}
{{switch colour multi | #B706A5 | Magenta     | Linear with two LED holes; the slider is tapered to accommodate the LEDs and has only one rear keycap mount recess<ref name="laugh" /> }}
{{switch colour multi | #FB7977 | Pink        | As with magenta, but tactile }}
|}

==Keyboards==

(Also see [[NMB Keyboards]])

*Some ADDS 1010 (white linear)<ref name="Ohaimark" />
*Early [[Commodore Amiga 500]] keyboards (white linear)
*Some [[Commodore Amiga 2000]] keyboards (white linear)
*Some [[Commodore PC-5/PC-10 keyboard]]s (white linear)
*[[Kroy 190]]
*[[Kroy 360]]
*Lynk PC122 (grey tactile, and possibly others)<ref name="webwit.lynk" />
*[[Memorex Telex NMB Hi-Tek]] (black, with brown or blue for space bar)
*NCR 4940 (white linear)
*[[NCR 4950]] (two-eye white or two-eye non-click black)
*[[NMB RT-100/RT-8200 series]] (wide variety)
*[https://deskthority.net/keyboards-f2/hi-tek-corp-history-t10435-60.html?hilit=nmb%20122#p305569 NMB HI-TEK Series 725 122-key] (white linear)
*[[Philips P2812]] (all white linear)
*Some Symbolics 365407 (grey and/or white)<ref name="Sym1" /><ref name="Sym2" />
*[[Televideo 725]]
*Unknown 122-key keyboard with NMB branded PCB (black, possibly clicky)<ref name="DT-UNK-122" />

==Gallery==
<gallery widths="250" heights="187">
File:NMB Hi-Tek caps.jpeg|Bottom view of some keycaps
File:Hi-Tek Tactile (Left) vs Hi-Tek Linear (Right) - Complete.jpg|Grey tactile (left) and neon green space bar linear (right)
File:Hi-Tek Linear (Left) vs Hi-Tek Tactile (Right) - Spring Height.jpg|Long space bar spring (left) vs normal spring (right)
File:NMB Springs - Tactile, Clicky, Spacebar.jpg|Spring comparison. From left to right: grey tactile, black clicky, neon green linear (space bar)
File:Hi-Tek Linear (Left) vs Hi-Tek Tactile (Right) - Contact Arms Outside.jpg|Linear/clicky and tactile contacts
File:Hi-Tek Linear (Left) vs Hi-Tek Tactile (Right) - Exploded.jpg|Disassembled linear and tactile switches; the long spring indicates a space bar switch
File:NMB Hi-Tek - Tactile vs Linear separators front.jpg|Comparison of contact separator bar widths between tactile (narrow, left) and linear (pictured) and clicky (wide, right)
</gallery>

===Linear===
<gallery widths="250" heights="187">
File:NMB Hi-Tek -- original design.jpg      | Original design
File:NMB Hi-Tek white.jpeg                  | White (linear) switch
File:NMB Hi-Tek white without slider.jpeg   | White switch internals
File:NMB Hi-Tek -- white two-eye linear.jpg | White two-eye click track slider with click arms omitted<ref name="Sandy-RT101-WL" />
</gallery>

===Tactile===
<gallery widths="250" heights="187">
File:NMB Hi-Tek -- grey tactile -- switches.jpg|Tactile grey switches from model RT 101+INTEL<ref>MouseFan — [http://mousefan.telcontar.net/image/intel.htm RT 101+INTEL]</ref>
File:NMB Hi-Tek -- grey tactile -- slider from below.jpg|Grey slider, inside view
File:NMB Hi-Tek -- grey tactile -- slider from side.jpg|Grey slider, side view
File:Hi-Tek Tactile - Closeup.jpg|Tactile contacts
File:Hi-Tek Tactile (Left) vs Hi-Tek Linear (Right) - Contact Arm Difference.jpg|Tactile contacts (left) vs linear/clicky contacts (right)
File:Hi-Tek Linear (Left) vs Hi-Tek Tactile (Right) - Internals 2.jpg|Linear/clicky and tactile contacts
</gallery>

===Clicky===
<gallery widths="250" heights="187">
File:NMB Hi-Tek -- black -- black with cyan for spacebar.jpg|Black switches with cyan for space bar, from RT8255CW+<ref>MouseFan — [http://mousefan.telcontar.net/image/rt8255.htm RT8255CW+ 104AT Thailand]</ref>
File:NMB Hi-Tek -- black -- black with cyan for spacebar (rear).jpg|Rear view of black and cyan, showing the click arms
File:NMB Hi-Tek - Trailing arm ramp.jpg|Ramp for the click arm at the rear of the slider
File:NMB Hi-Tek - Switch Front Blue Spacebar.jpg|Top of a blue slider
File:NMB Hi-Tek - Switch Front Black.jpg|Top of a black slider
File:NMB Hi-Tek - Switch Front - Bigger Eyes.jpg|Black switches, larger "eye" variant
File:NMB Hi-Tek - Internals Front.jpg|Black (clicky) switch internals as seen from the front
File:NMB Hi-Tek - Internals Back.jpg|Black switch internals as seen from the rear, including the click arm
File:NMB Hi-Tek -- click arm (side view).jpg|Side view of the click arm
</gallery>

===Integrated LED===
<gallery widths="250" heights="187">
File:NMB Hi-Tek -- white integrated LED.jpg|Later design, clicky version (centre)
</gallery>

==External links==

*Sandy — [http://sandy55.fc2web.com/keyboard/nmb_hitek_sw.html NMB HI-TEK Key Switch and Keyboard sorted by Chronological Order]

==References==
<references>
<ref name="Commodore">Deskthority — [http://deskthority.net/marketplace-f11/commodore-mechanical-keyboard-hi-tek-switches-t5523.html Commodore mechanical keyboard (Hi-Tek switches)]</ref>
<ref name="Sym1">Deskthority — [http://deskthority.net/keyboards-f2/the-lisp-keyboards-t98.html#p1149 The Lisp keyboards]</ref>
<ref name="Sym2">Abstract Science Ltd — [http://www.asl.dsl.pipex.com/symbolics/photos/IO/inside-keyboard.html Symbolics Keyboard internals (PN 365407 Rev C)]</ref>
<ref name="webwit.lynk">webwit.nl — [http://webwit.nl/input/lynk/ Index of /input/lynk]</ref>
<ref name="rzwv-sliders">ちゃたりたいね — [http://kbd.rzw.jp/chata/slider_in_page/ All Slider List.]</ref>
<ref name="gh-RT101-white-click">geekhack — [http://geekhack.org/index.php?topic=48305 Good Buy? NMB and Black Alps]</ref>
<ref name="DT-white-linear">Deskthority — [http://deskthority.net/marketplace-f11/price-check-how-much-is-my-worth-t16-900.html#p89822 Price Check: How much is my _____ worth?]</ref>
<ref name="Sandy-N-97-KANA">Sandy — [http://sandy55.fc2web.com/keyboard/n-97_kana.html N-97 KANA]</ref>
<ref name="Sandy-RT101-WL">Sandy — [http://sandy55.fc2web.com/keyboard/rt101-LC-WL.html NMB RT101+ WL]</ref>
<ref name="P2812">Deskthority — [http://deskthority.net/photos-videos-f8/philips-p2812-t4798.html#p91696 Philips P2812]</ref>
<ref name="laugh">Deskthority — [http://deskthority.net/keyboards-f2/hi-tek-were-having-a-laugh-t6482.html Hi-Tek were having a laugh]</ref>
<ref name="KBDMania-Memorex">KBDMania — [http://www1.kbdmania.net/xe/review/1283663 NMB MEMOREX]</ref>
<ref name="DT-UNK-122">Deskthority — [http://deskthority.net/keyboards-f2/hi-tek-corp-history-t10435-30.html#p232822 Hi-Tek Corp. History]</ref>
<ref name="Ohaimark">Deskthority — [https://deskthority.net/viewtopic.php?t=14796 Ohaimark's Collection]</ref>
</references>

[[Category:NMB switches]]
[[Category:Hi-Tek Corporation switches]]
[[Category:Clicky switches]]
[[Category:Tactile switches]]
[[Category:Linear switches]]
[[Category:Alternate action switches]]
[[Category:Metal contact switches]]
[[Category:List of all keyboard switches]]