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Title: Remote two-wire data entry method and device

A device for detecting switch closure such as in a keypad for entering data comprising a matrix of conductor pairs and switches, each pair of conductors shorted by the pressing of a particular switch, and current-regulating devices on each conductor for limiting current in one direction and passing it without limit in the other direction. The device is driven by alternating current. The ends of the conductors in a conductor pair limit current of opposing polarities with respect to each other so that the signal on a shorted pair is an alternating current signal with a unique combination of a positive and a negative peak, which, when analyzed, allows the determination of which key was pressed. The binary identification of the pressed key is passed to the input port of a host device.
  1. (Aiken, SC)
Issue Date:
OSTI Identifier:
United States of America as represented by United States (Washington, DC) SRS
Patent Number(s):
US 5424731
Contract Number:
Research Org:
Country of Publication:
United States
remote; two-wire; data; entry; method; device; detecting; switch; closure; keypad; entering; comprising; matrix; conductor; pairs; switches; pair; conductors; shorted; pressing; particular; current-regulating; devices; limiting; current; direction; passing; limit; driven; alternating; opposing; polarities; respect; signal; unique; combination; positive; negative; peak; analyzed; allows; determination; key; pressed; binary; identification; passed; input; host; regulating device; alternating current; current signal; negative peak; opposing polarities; data entry; limiting current; /341/