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MEI Mercutronic keyboards

Contents

Overview

Mercutronic keyboards from Mechanical Enterprises use MEI’s Mercutronic (or “Mercutron”) mercury-contact switches. The original application of the mercury-filled tube concept to keyboards was the Mercutronic encoding switch, but keyboards were produced with both encoding and non-encoding switches. Such a keyboard has yet to be encountered; Jacob Alexander noted over on Deskthority that “mercury filled tube switches … had to be disposed of due to fear of mercury poisoning leaking out of the rubber tubes”, with no mention of who made such keyboards or how he came across this information. Such a claim could only hold true for anyone who was aware that their keyboard contained mercury switches, and further who was motivated to dispose of them.

Mercutronic Coding Keyboards

Two Mercutronic encoding keyboards were depicted in Electronic Design magazine in October 1969, albeit only from the outside. (The internal structure is depicted in the advertisement, but only as a diagram.) These keyboards used solderless switches connected to a common bus by contact pressure alone, using gold-plated diode leads to prevent corrosion. An advertisment in Electronic Design from July 1970 depicts a variety of Mercutronic Coding Keyboards, ranging in size from a 5-key BCD-encoded unit up to a full 63-key conventional keyboard. These keyboards were likely to be short-lived due to the move towards matrix scanning encoding that took place at the start of the 1970s, rendering keyboards with self-encoding switches (and those with diode matrices) obsolete.

An advertisement in the Electronic Engineer from November 1970 shows a pair of keypads (12-key and 10-key) which replaced the conductive ribbon bus with PCB tracks; the switches are screwed to the PCB instead of snapped into the aluminium extrusion used in the original design. Replacing the aluminium mounting frame and ribbon with a PCB was said to reduce the cost by 5–10% in production quantities.

SS-based keyboards

An advertisement in Electronic Design from November 1972 shows a keyboard that uses SS-11 non-encoding, PCB-mounted switches. Unfortunately, the encoding method is not stated (only that “several methods of encoding” were available), and the photograph is too small to see any details clearly.

Documentation

All documents were scanned by Bitsavers unless otherwise noted.