Datanetics elastic diaphragm array
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Datanetics elastic diaphragm array is a membrane keyboard system based on their elastic diaphragm technology. The series has no official name, but in the DC Series Data Entry Keyboards brochure from 1976 it was described as a "batch fabricated array" in comparison to the modular DC-50 series that followed it. In that brochure, published after DC-50 was introduced, the membrane array system is shown as a flat keypad without keycaps (similar to the keypad on a microwave oven), but the option of adding actuator assemblies is mentioned, which is how it was used prior to the introduction of discrete switches.
Datanetics elastic diaphragm array was introduced around 1968, using a complex membrane sandwich with gold plated contact surfaces, and arranged above a PCB. Two patents are known: US3594684 covers the membrane system, and US3773997 covers a lost motion actuator. This second patent includes a diagram of the force curve.
The elastic diaphragm switch was subsequently adapted into a discrete switch module, which was introduced a few years later in 1973 as DC-50 series. Such switches contain a small single-key membrane unit without a PCB.