Fujitsu Magnetic Reed

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Fujitsu
Magnetic Reed Switch
(Vertical Reed)
Manufacturer Fujitsu
Switch type Linear / Tactile
Sense method Magnetic reed
Fujitsu
Magnetic Reed Switch
(Cross Reed)
Manufacturer Fujitsu
Switch type Linear
Sense method Magnetic reed
Peak force 35 cN?

History

Until the early 80s, Fujitsu used magnetic reed switches in some of the keyboards produced. After the invention of their leaf spring switch, Fujitsu seemed to discontinue all uses of magnetic reeds in keyboard switches.

In 1968, Toshito Hara of Fujitsu, filed for a patent on sealed magnetic reed switch improvements which by far pre-dates any of the known keyboards and electric typewriters made by Fujitsu.[1] Currently, there are two known keyboards Fujitsu keyboards that utilized reed switches. Each with a different switch design (and even variation) and neither with a known patent. However, the style of keycap and slider of each design somewhat mirrors the 1st generation Fujitsu leaf spring switch, and the second; parts of the 1st, and more of the 2nd.

Interesting to note, is that while these switches are linear, the contact of the reed is audible. The sound is not generally consistent between switches, nor is to the same level as purposefully audible keyboard switches such as a Cherry MX Blue keyswitch.

Known keyboards:

Vertical reed

Each reed is positioned vertically inside the keyswitch. To actuate the reed, the magnet is moved alongside the sealed reed switch, which will cause the reeds to both pull towards the magnet. The reed switch is designed such that the contact point is lower in the keypress (~60% of a keypress), mimicking a typical mechanical keyswitch. The magnet itself is oriented either North or South pointing to the top of the switch, in order to properly magnetize the reed when the distance to the switching point decreases. The resistance of the switch is provided by a single coil spring.

A cross slider is used in most of the switches, except switches that had LEDs under the keycap. These switches used a very primitive version of cross reed slider.

Key feel

Linear, extremely smooth. There is virtually no friction present in the mechanism. The switches also have a very low actuation force. Switches with LEDs in them are a bit stiffer.

A tactile version also exists. The tactile leaf in this switches causes more friction, as well as a much stiffer keyfeel.

Keycaps

All known keycaps are spherical double-shots made of nearly solid plastic. They use a cruciform slider, like many of the switches from the late 1970's through the 1980's do. Keycaps are similar if not identical to those found on 1st generation Fujitsu leaf spring switches.

Fujitsu N860-8282

A tactile vertical magnetic reed switch variant was discovered in the Fujitsu N860-8282:

Cross reed

In contrast to the vertical reed switch, the reed is placed parallel to the metal plate across the diagonal. This reduces the overall needed height for the keyswitch module. While there are 3 pins to the switch, 2 of the pins are connected together. The three pin design is suspected to aid in switch rigidity (especially needed during keycap removal).

Key feel

Very smooth linear actuation, with a rubber stopper on some larger keys. Has a very light keypress.

Keycaps

All known keycaps are spherical double shots, some of them with filled engravings. They fit directly onto the slider the same way the legends fit onto two piece IBM buckling spring keycaps. The fit on the sliders is exceedingly tight (enough to painfully pinch your fingers when replacing the keycaps), and thus it takes skillful use of a screwdriver (or equivalent tool) to pry off the keycap. Thick plastic is used. Keycaps are not compatible with Vertical reed switches; they are similar if not identical to those found on 2nd generation Fujitsu leaf spring switches.

Availability

Not much is known about these switches, other than they disappeared around the time Fujitsu Leaf Spring switches started to show up. Only Fujitsu is known to have manufactured these switches.

Interesting facts

  • Old Fujitsu keyboards often have a red grounding sticker on the mounting plate. This is generally indicative of the keyboard using Fujitsu magnetic reed switches, although at least one example is known where Fujitsu leaf spring switches were used instead.

External links

References

  1. Patent US3541483 — Toshito Hara Magnetic Reed Switch Improvement Patent
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 MouseFan — N860-9201-T001 03B Fujitsu Vertical Reed Keyboard Last updated 2005-10-04. Retrieved 2015-07-25.