Touch pad and display tube circuitry

摘要

Improved touch pad and display tube circuitry including a touch pad circuit, a tube circuit, and a scan voltage pulse drive circuit for generating scan voltage pulses applied to the touch pad and display tube circuits. The touch pad circuit receives scanning voltage pulses having very fast rise-times, to reduce the effects of contaminants which may be present on the surface of the touch pad panel. The display tubes of the display tube circuit each include an anode, a plurality of display cathodes and a control cathode. The current flowing through the control cathode is proportional to the current in the associated display cathodes. The control cathode current is utilized by the drive circuit to adjust to a desired value the value of the magnitude of the scan voltage pulses applied to the anodes of the display tubes. The drive circuit utilizes a substantial portion of common circuitry to generate both the touch pad and display tube scan voltage pulses. The control circuit also functions to isolate the touch pads and display tube anodes in such manner that the fast rise-time pulses applied to the touch pads are not coupled to the display tube anodes.