Hi-Tek Series 725
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This article requires restructuring — Colour tables are obsolete; colour table needs converting to variants table and the remainder of the page needs restructuring into a less disjointed arrangement |
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| Manufacturer | Hi-Tek |
|---|---|
| Introduced | 1983 |
| Discontinued | 1995 or later |
| Switch type |
Clicky Tactile Linear Latching |
| Sense method | Metal leaf |
| Patents | EP0124206 (1984) |
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 videogame from 1978. 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.
Contents
Description
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.[1] The age of the keyboard can be estimated by the lack of dedicated LED switches.[2]
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.[3]
Series 725 switches also use custom stabilisers where the custom-shaped stabiliser wire clips directly under the switch shell.[4] 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.[5] The NMB RT8255+ with Windows keys indicates that they were produced at least 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.[6] 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.
Original design
White (linear) switch
White switch internals
White two-eye click track slider with click arms omitted[7]
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 keys; notwithstanding the different colour and slider planform, the difference with these switches is not known.
Tactile grey switches from model RT 101+INTEL[8]
Grey slider, inside view
Grey slider, side view
Tactile contacts
Tactile contacts (left) vs linear/clicky contacts (right)
Linear/clicky and tactile contacts
_vs_Hi-Tek_Linear_(Right)_-_Contact_Arm_Difference.jpg)
_vs_Hi-Tek_Tactile_(Right)_-_Internals_2.jpg)
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.[9] 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.
Black switches with cyan for space bar, from RT8255CW+[10]
Rear view of black and cyan, showing the click arms
Ramp for the click arm at the rear of the slider
Top of a blue slider
Top of a black slider
Black switches, larger "eye" variant
Black (clicky) switch internals as seen from the front
Black switch internals as seen from the rear, including the click arm
Side view of the click arm
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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.[11]
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
| White | Linear (one[12] or two[13][7] eyes) Clicky (two eyes)[14]; white switches used for space bar will have a longer spring to increase resistance[15] with the space bar slider marked with a dot[14] as seen on the Philips P2812 Clicky, with tapered planform and LED holes[16] | |
| Yellow | Linear; reported to be slightly lighter weight than white[11] | |
| Grey | Tactile (two eyes) Linear (one eye)[17] Linear (two eyes) | |
| Beige | Linear (two eyes)[18] Tactile (one eye) [19] Clicky (presumably); used for space bar switch with powder blue switches[16] | |
| Neon green | Linear; used for space bars on linear and tactile boards | |
| Sea green | Appears to be linear; purpose unknown, probably another space bar switch[20] | |
| Black | Clicky (two eyes; 45 g tactile force, 85 g terminal force[21]) Tactile (two eyes)[11] Latching action (centre eye)[11] | |
| Powder blue | Clicky[16] | |
| Cyan | Clicky; for space bars on clicky boards, and has a longer spring to increase resistance | |
| Blue | Variant of the above | |
| Brown | Variant of the above (85 g tactile force, 100 g terminal force[21]) | |
| Magenta | Linear with two LED holes; the slider is tapered to accommodate the LEDs and has only one rear keycap mount recess[11] | |
| Pink | As with magenta, but tactile |
Keyboards
(Also see NMB Keyboards)
- Some ADDS 1010 (white linear)[22]
- Early Commodore Amiga 500 keyboards (white linear)
- Some Commodore Amiga 2000 keyboards (white linear)
- Some Commodore PC-5/PC-10 keyboards (white linear)
- Kroy 190
- Kroy 360
- Lynk PC122 (grey tactile, and possibly others)[23]
- 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)
- NMB HI-TEK Series 725 122-key (white linear)
- Philips P2812 (all white linear)
- Some Symbolics 365407 (grey and/or white)[24][17]
- Televideo 725
- Unknown 122-key keyboard with NMB branded PCB (black, possibly clicky)[25]
Gallery
Bottom view of some keycaps
Grey tactile (left) and neon green space bar linear (right)
Long space bar spring (left) vs normal spring (right)
Spring comparison. From left to right: grey tactile, black clicky, neon green linear (space bar)
Linear/clicky and tactile contacts
Disassembled linear and tactile switches; the long spring indicates a space bar switch
Comparison of contact separator bar widths between tactile (narrow, left) and linear (pictured) and clicky (wide, right)
_vs_Hi-Tek_Linear_(Right)_-_Complete.jpg)
_vs_Hi-Tek_Tactile_(Right)_-_Spring_Height.jpg)
_vs_Hi-Tek_Tactile_(Right)_-_Contact_Arms_Outside.jpg)
_vs_Hi-Tek_Tactile_(Right)_-_Exploded.jpg)
References
- ↑ Geekhack — What did you get in the mail today? Posted 2014-08-26. Retrieved 2024-03-29.
- ↑ Geekhack — NMB Hi-Tek Space Invaders discussion topic Posted 2014-10-13. Retrieved 2024-03-29.
- ↑ Geekhack — Nmb rt-8251t Posted 2010-11-19. Retrieved 2024-03-29.
- ↑ Deskthority — NMB RT101+ Posted 2012-10-15. Retrieved 2024-03-29.
- ↑ Deskthority — Picked up an XT keyboard the other day Posted 2012-09-18. Retrieved 2024-03-29.
- ↑ Geekhack — Weird keyboard is here. Posted 2008-11-18. Retrieved 2024-03-29.
- ↑ 7.0 7.1 Sandy — NMB RT101+ WL (Japanese) Retrieved 2024-03-29.
- ↑ MouseFan — RT 101+INTEL (Japanese) Retrieved 2024-03-29.
- ↑ YouTube — NMB Hi-Tek Trailing arm click Dated 2013-01-12. Retrieved 2024-03-29.
- ↑ MouseFan — RT8255CW+ 104AT Thailand (Japanese) Dated 2003-10-13. Retrieved 2024-03-29.
- ↑ 11.0 11.1 11.2 11.3 11.4 Deskthority — Hi-Tek were having a laugh Posted 2013-09-09. Retrieved 2024-03-29.
- ↑ Deskthority — Price Check: How much is my _____ worth? (NOTE: Pictures lost!) Posted 2012-12-20. Retrieved 2024-03-29.
- ↑ Sandy — N-97 KANA (Japanese) Retrieved 2024-03-29.
- ↑ 14.0 14.1 Geekhack — Good Buy? NMB and Black Alps Posted 2013-09-09. Retrieved 2024-03-29.
- ↑ Deskthority — Philips P2812 Dated 2013-01-07. Retrieved 2024-03-29.
- ↑ 16.0 16.1 16.2 Sandy — RT-101+ Retrieved 2024-03-29.
- ↑ 17.0 17.1 Abstract Science Ltd — Symbolics Keyboard internals (PN 365407 Rev C) (Wayback Machine) Archived 2011-03-17.
- ↑
Deskthority — Commodore mechanical keyboard (Hi-Tek switches)(DEAD!) - ↑ ちゃたりたいね — All Slider List. (Wayback Machine) Archived 2014-09-27.
- ↑ AliExpress — Buy 7pcs/ Bag HITEK Keyboard switch green and fluorescence … (German) (Wayback Machine) Archived 2019-04-14.
- ↑ 21.0 21.1 KBDMania — NMB MEMOREX (Korean) (Wayback Machine) Archived 2010-11-25.
- ↑ Deskthority — Ohaimark's Collection Posted 2016-10-16. Retrieved 2024-03-29.
- ↑ webwit.nl — Index of /input/lynk Retrieved 2024-03-29.
- ↑ Deskthority — The Lisp keyboards Posted 2011-02-07. Retrieved 2024-03-29.
- ↑ Deskthority — Hi-Tek Corp. History Posted 2015-05-28. Retrieved 2024-03-29.
External links
- Sandy — NMB HI-TEK Key Switch and Keyboard sorted by Chronological Order Dated 2014-01-18. Retrieved 2024-03-29.
