Importance

Loading Importance Indicators...

Abstract

An N-Key Rollover Type Keyboard sequentially scans the keys so as to transmit information correctly as to each key which is depressed without transmitting a garbled code which could result from simultaneous depression of two keys without the sequential scanning. The coded information from the keyboard is applied to a differential amplifier along with the noise signal from the keyboard so that only the coded signal is amplified, thus reducing the noise level quite markedly. The coded signal is fed to a shift register which is cycled once for each scanning of the keyboard so that a current scan can be compared with a past scan in a comparator or an AND gate with the result that there will be an output only for the first scan that detects a depressed key, i.e., the depression of the key will not cause continued signal transmission, but will cause such transmission once only. A strobe is generated only on the first scan. In addition, the keyboard is provided with various function keys which generate single channel non-coded output signals. A strobe inhibit circuit is provided to prevent strobing when a function key is depressed.

Loading the Abstract Image...

First Claim