Unimax Switch Corp
Currently known as Wallingford Property Holdings, Inc., the Connecticut company that would become known as Unimax Switch Corporation was founded on the 5th of March 1949. Its previous names were the Unadco Manufacturing Company, the United Manufacturing Company and Unimax Switch Corporation. (A separate and related Unimax Corporation was created in Delaware, with branches in New York, North Carolina, Missouri, Texas, Arizona and Connecticut.) Unimax Switch is reported by a current employee to have been sold off at some point in the 1980s or possibly earlier.
Unimax Switch Corp advertised literature for a pulse output switch type in the Electronic Engineer magazine in November 1970. This switch design produced a millisecond pulse upon actuation. No further details were given and, while patents for Unimax Switch are available, there are none that appear to cover keyboard switches.
A clearer description is given in the In key with computers panel of the article Capacitive keys, simpler circuits add up to reliable keyboard from Electronics magazine, Vol. 43 No. 25, 7th December 1970:
Unimax Switch of Wallingford, Conn., offers a keyboard with a “flying magnet” key. The key contains two magnets with their poles in opposition. Each opposed pole resets against a metal strip, with a third strip between them. When the key is depressed, the upper magnet’s strip is pushed in contact with the center strip, repelling the lower magnet. The lower strip snaps up to contact the middle strip momentarily. When the three strips touch, a signal is transmitted in two parts—a three-bit and a four-bit segment—to flip-flop circuitry for encoding. The lower magnet returns to its original position in 2 milliseconds, drawing the lower strip away and breaking the electrical contact.
This description depicts an implementation very similar to that of Magsat’s “flying magnet” switches. While Magsat placed visual advertisements and price lists for their switches, Unimax’s switches seem to have disappeared. It’s curious that both Magsat and Unimax were from Connecticut.
- Digital switch module advertisement, The Electronic Engineer, Vol. 29 No. 11, November 1970