US Patent 5,406,843 - Digital Liquid Level Sensing Apparatus
US Patent 5,613,399 - Method for Liquid Level Detection
US Patent 6,018,335 - Programmable Keyboard and Method
US Patent 6,125,696 - Digital Liquid Level Sensing Apparatus
US Patent 6,138,508 - Digital Liquid Level Sensing Apparatus
US Patent 6,240,778 - Liquid Level Point Switch Sensor
