| 摘要 |
<p>A device is used for coding a switching element field, e.g. the input keyboard of a data processing device. It is designed to incorporate electronic hysteresis whilst using a minimum of integrated circuitry. Hysteresis ensures that a key must be depressed for a sufficient time before having an input effect so as to eliminate data keying errors. The switching elements have negligible impedance in the closed position and high impedance when open. A circuit connected to the switch matrix, a coltage source, and a signal amplitude detector (20), conducts a periodic assessment of the switch conditions which are different voltages according to the switch positions. The conditions are stored, and when a closed switch is detected the detector sensitivity for that switch is altered.</p> |
