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HP48 Keyboard Scanning and Electrical Resistance - Printable Version

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HP48 Keyboard Scanning and Electrical Resistance - Thomas Chrapkiewicz - 03-17-2008

The keyboard of the HP48 is scanned as somewhat documented in the available schematics.

Can anyone explain (or direct me to the appropriate links) why the keyboard contact paths have a significant (kilohms) electrical resistance?

Regards,
TomCee


Re: HP48 Keyboard Scanning and Electrical Resistance - Randy - 03-17-2008

Documented in US Patent 5,065,356.

You'll find a copy posted on Eric's site here: PDF of HP Patent 5,065,356


Re: HP48 Keyboard Scanning and Electrical Resistance - Thomas Chrapkiewicz - 03-18-2008

Randy:
Excellent resource! Thank you very much!
TomC