Burroughs Opto-Electric

This article requires additional photographic illustration — photos with clean metal plates would be desirable

Burroughs opto-electric with torsion spring

Manufacturer	Burroughs
Inventor	Craig C. Madsen Daniel B. Stewart James Andree
Switch type	Parabolic
Sense method	Optoelectronic
Rated lifetime	Unknown
Peak force	35 g, 60 g, 130 g
Patents	US4301345 (1980) US4479111 (1982)

History

Developed by Burroughs in the early 1980s as a "low profile", "tactile" and consistent switch using an optoelectronic switching mechanism (note that it's not tactile in the modern sense). Besides being a rare optoelectronic switch, this switch uses a horizontally disposed biasing spring which gives a very unique feel to the key actuation.

Only one keyboard is known to have been built with these switches for the Burroughs by Kokusai Electric: the BET-KB.

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  Exploded view of switch.
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  Dirty grey dye sublimation keycap, and underside of cap locks key.
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  Dirty blue legendable keycap, pad printed.
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  Single spring splider, view of torsion spring. Metal plate is both very dirty and heavily corroded.
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  Double spring slider, approximately 130 g.
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  Underside of sliders attached to metal plate.
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  LED and photo resistor for each torsion spring slider.
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  Clean keycaps, top row uses heavy switches, approximately 130 g.

Keyfeel

Very smooth slider, and very consistent spring. Since the optoelectronic is contact-less, it plays no part in the keyfeel. The horizontally disposed biasing spring provides a very unique key feel, as the force to actuate actually decreases past a certain point in the key press.

Keycaps

All known keycaps are dye sublimated. Except for those with replaceable key-legends, which are pad printed.

Availability

Only one keyboard is known to have been made with these switches: the BET-KB

Patents

• Patent US4479111 — Photo-Optical Switch Apparatus
• Patent US4301345 — Key switch actuation by torsion spring (Has force curves for the horizontally disposed biasing spring)