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George Risk Industries switches

Contents

Overview

George Risk Industries (GRI) produce reed keyboard switches in-house. They also re-sold Far East–made keyboard switches under their own series names. Confirmation of the latter came from an anonymous ex-employee, who had mentioned that they purchased switches from “Asia”. The Far East–made types are no longer advertised for sale, presumably because they are no longer manufactured by the suppliers.

Most of the Far East switches were sourced from Futaba; these are the KBR reed type and the KBM and KBM-LP mechanical types. KBM-DIN however appears to be Mitsumi KLT series. While Futaba’s first generation switches were universally unbranded (with branding added only to the later MA series), Mitsumi’s switches were all branded, so it remains to be seen whether KBM-DIN was branded. Some KBM switches were however sold with GRI branding in a custom colour scheme.

Series KB

Series KB comprises tall, cylindral reed switches (1.75″ from base to keycap centre), secured with a nut onto a threaded leg. They support double-pole and normally closed configurations and lamp illumination; the rated lifetime is 50 million cycles.

Series KBPS

This is similar to KB, but designed to be attached to a front panel with a nut above and below the panel. The operating force codes within the part number generally denote higher forces than they do for KB series:

Code Force (KB) Force (KBPS)
01 2.5 oz (71 gf)
02 4.0 oz (113 gf) 5.0 oz (142 gf)
03 6.0 oz (170 gf) 8.0 oz (227 gf)
04 15.0 oz (425 gf)

These codes are not mnemonic, as they are with Micro Switch series.

Series KBLP

Series KBLP reed switchces are lower in profile (1.375″ from base to keycap centre) and square in section, but remain secured with a nut onto a threaded leg. The lifetime remains 50 million.

Series KBR

These are Futaba-made reed switches; only known to be single-pole momentary non-illuminated; lifetime 30 million. The GRI site did not list these in 1998, the oldest archived copy in the Wayback Machine.

US patent 4041427, issued to Futaba in 1977 and filed in 1975, appears to be for these switches, although curiously they are shown with a square-section shell instead of a truncated cylindrical shell. The patent also depicts straight-mount switches, while GRI KBR is cruciform mount.

KBR appears to be Futaba’s MR series, which was previously mistaken for being mechanical due to an incorrect photo being published by ePartsHub and ECPlaza. The diagrams and specifications are a match.

Series KBM

These are Futaba-made mechanical switches (Futaba MD series), available in single pole momentary and alternate action forms. The rated lifetime is 10 million cycles. KBM is listed as being available in a latching variety, which at the time of writing may yet be undiscovered in a GRI keyboard.

Depictions and descriptions of KBM vary. In 1978, keyboard model 756 was advertised as having “IBM series key switches”, which makes little sense. In Interface Age, November 1977, KBM is depicted as a Futaba switch. In Interface Age, February 1977, they are depicted as what seems to be ultra-low-profile switches that barely protrude past the keycap, but it seems that the wrong photograph was used. However, no correction was made in the next issue. The description was given as follows:

Build custom keyboards in minutes with the KBM series keyswitch. The model KBM is a low-cost, long life keyboard switch ideal for use in CRT terminals, data entry devices, hex keypads, touch tone encoders, etc. Semi-sealed construction means immunity to environmental contamination and the gold crosspoint contacts insure reliable, low bounce switching for more than 10 million operations. Contacts are rated at 12 volts, 1 ma, with less than 100 milliohms contact resistance. Mounting through an easily fabricated metal panel insures precise keycap alignment, and the rugged 1/16″ terminals make hardwired prototypes a breeze.

The mention of “gold crosspoint” appears to be another error, because Futaba MD is not crosspoint contact; rather, a pair of flat contact leaves with gold plating are brought down over a pair of gold-plated dome-shaped pressings. Additionally, KBM terminals are documented as 0.047″ (the same as the terminals on Futaba MD-4PCS measure, around 1/21.25″), while the advertised 1/16″ is larger at 0.0625″.

Futaba MD switches can have up to three colours: the plunger (typically clear or black), shell (typically cream or black) and base plug (typically matching cream or black, or contrasting orange or yellow). The meaning of the colour code is not yet known, but it seems to indicate at least in part the weighting of the switch.

Keyboards with KBM switches have been found with several colour codes, suggesting that different switch weights were offered, although there is no documented evidence of this, with only two models known. The model numbers do easily allow for additional models to exist. GRI also had custom-branded KBM 01 01 switches produced, with a white shell and black base.

The datasheet for KBM cites 0.03±0.01″ pretravel and 0.12±0.01″ total travel and a 3.5±0.8 oz operating force.

Model Type NSN
KBM-01-01 Momentary 5930-01-121-7871
KBM-01-01-AA Alternate action

Series KBM-LP

These are Futaba-made low-profile mechanical switch (Futaba ML series), available in single pole momentary forms only. The rated lifetime is 3 million cycles. It remains unclear whether illuminated forms existed in Futaba ML and sealed linear series. Where GRI needed KBM-LP illuminated keys, they simply snapped or sawed off a corner of the switch to make room for the LED.

Only one part number is known, KBM-LP. This is cited as 0.045±0.01″ pretravel, but a total travel of only 0.01±0.02″.

Series KBM-DIN

Unknown mechanical type; appears to be Mitsumi KLT series on the basis of the appearance in diagrams and that it is stated as being tactile. These were also not listed for sale in 1998; there is no record of these ever being sold separately.

The specifications are given as follows for Model 3075 keyboard and Model 3032 keypad:

Parameter US Metric equiv.
Total travel 0.157±0.020″ 3.99±0.51 mm
Pretravel 0.100±0.005″ 2.54±0.13 mm
Operating force 1.23±0.35 oz 34.9±9.9 gf

Documentation