Circuit for reducing electromagnetic interference from magnetic core keyboards
US4665461A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 6, 1986 |
| Grant date | May 12, 1987 |
| Priority date | — |
| Expiry date | Mar 6, 2006 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S84/07
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The present disclosure describes circuit variants for reducing electromagnetic interference from saturable core keyboards to acceptable levels. The invention finds particular application in conjunction with capacitive-discharge scan techniques used in such keyboards. In order to attenuate the external field resulting from such techniques, a circuit is taught which effectively disconnects the scan line array from the capacitor charging circuit during the time between scans. A second variant, when added to the first, further reduces interference by disconnecting the entire scan circuit from the supply potential during the scan time thereby eliminating steady-state currents and turnoff oscillatory transients.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.