Abstract: An electronic learning/teaching device operates with and without a printed sheet element having an arrangement of selectable content by means of a user responsive sensor array beneath a surface configured to receive the element. The sensor array is formed by cross-points of two sets of crossing conductive lines, one set being driven sequentially with a radio frequency square wave and the other set being sampled sequentially though a high impedance amplifier connection with an asynchronous detection circuit. Where more than one cross-point location is user activated, algorithms are used to identify one cross-point sensor location as the user activated selection.

Abstract: A pressure relief nozzle installs on the face of a drill bit, and provides a flow path for drilling fluid. The pressure relief nozzle has a larger internal flow area when flow rates through the drill bit are high, and a smaller flow area when flow rates are low. Upon reduction of the pressure relief nozzle's internal flow area, the pressure drop across the drill bit tends to stabilize due to the reduced flow area through the drill bit.

Abstract: Presented is a communications protocol for use by interconnected hazardous condition detectors, such as smoke and carbon monoxide detectors for use in dwellings and other structures. This communications protocol provides conventional signaling to indicate the presence of a smoke condition necessitating the generation of a smoke temporal pattern by all interconnected detectors. The protocol further defines a signaling method by which conventional smoke detectors that are incapable of providing temporal patterns other than that required for a smoke alarm condition will not be sent into an alarm mode of operation upon receipt of a signal other than the conventional smoke alarm signal. This communications protocol defines a pulsed signal to indicate a non-smoke alarm condition that is of a duration that will not trigger the conventional smoke alarms.

Abstract: An apparatus and method for monitoring voltage on a LAN cable on which data is conveyed by negative-going pulses. Positive voltage on the LAN cable is interpreted as noise. Positive voltage is detected by, for example, comparing the voltage on the LAN cable to a positive reference voltage, determining the peak positive voltage on the LAN cable, or determining the average positive voltage on the LAN cable. Upon the detection of positive voltage on the LAN cable, the presence (and possibly the amount) of noise is indicated to a person or data processing system which supervises the LAN called a LAN sentinel. The apparatus or method could be implemented in a Media Attachment Unit (MAU) with audio, visual or electronic noise indication means. Alternatively, it could be implemented as a hand-held diagnostic tool.