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RFI Suppression in a Keyboard

IP.com Disclosure Number: IPCOM000050246D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

McLaughlin, R: AUTHOR

Abstract

Certain known types of keyboards operate on the electronic concept of a capacitive coupling change and sensing that change. When such keyboards are operated in the presence of a strong modulated radio frequency, such as in the order of 30 to 60 volts/meter, the radio frequency interference (RFI) can cause the keyboard to function improperly. This is because the radio frequencies are coupled from the computer operator through the key buttons and then to the circuits that sense the capacitive charge.

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RFI Suppression in a Keyboard

Certain known types of keyboards operate on the electronic concept of a capacitive coupling change and sensing that change. When such keyboards are operated in the presence of a strong modulated radio frequency, such as in the order of 30 to 60 volts/meter, the radio frequency interference (RFI) can cause the keyboard to function improperly. This is because the radio frequencies are coupled from the computer operator through the key buttons and then to the circuits that sense the capacitive charge.

Referring to the figure, a small conical stainless steel spring 10 is installed between each of the key stems 12 and the metal keyboard assembly 14. The radio frequency interference energy is then channeled from plastic key button 13 through the key stem 12 and to the metal keyboard 14 and to ground.

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