Abstract: A digital-to-analog converting apparatus having a plurality of stages arranged in a series. Each stage includes a latch for storing one of the bits of a digital input signal. Each stage includes a resistance, the resistances of the stages being connected in series. One end of the resistance in the first stage is connected to a reference voltage equal to the mid-point of the voltage range of the analog output signal to be produced. Constant current sources, of equal value in each stage, are connected to each end of the resistance and through a current switch to a constant current sink. The current switch is controlled by the outputs of the latch of the stage so that a constant current flows through the resistance in one direction or the other, increasing or decreasing the voltage applied to the next resistance in the series depending upon whether the stored bit is a logic 1 or a logic 0.

Abstract: An analog-to-digital converting apparatus having a plurality of stages arranged in series, each stage including a comparator. The positive input terminals of all the comparators are connected in common to the analog signal input terminal. The negative input terminal of the first comparator in the series is connected to a reference voltage equal to the mid-point of the voltage range of the analog input signals. Each stage except the last has a resistance connected between the negative input terminal of its comparator and that of the next comparator in the series. Constant current sources, of equal value in each stage, are connected to each end of the resistance and through a current switch to a constant current sink. The current switch is conrolled by the output of the comparator of the stage so that a constant current flows through the resistance in one direction or the other, increasing or decreasing the voltage at the negative input terminal of the next comparator in the series.

Abstract: Sensing apparatus for monitoring the passage of objects, including people, through a doorway. A source of radiant energy is positioned at one side of the doorway and two spaced-apart detectors are positioned at the opposite side to receive beams of radiant energy from the source. A receiver is connected to each detector and produces a signal indicating whether the beam of radiation from the source is impinging on its associated detector or is being blocked by a passing object. Logic circuitry responds to the signals from the receivers and produces a first or second output condition depending upon which beam from the source is the last one to be interrupted by a passing object.

Abstract: Sensing apparatus for monitoring the operation of an electrical appliance. The sensing apparatus is plugged into a standard electrical outlet and the appliance to be monitored is plugged into the sensing apparatus. The appliance current flows through a transformer in the sensing apparatus. Detection circuitry including a comparator produces one signal when current flow through the transformer is negligible (appliance off) and another signal when the current flow through the transformer is significant (appliance on). Transistor circuitry connected to the detection circuitry produces a pulse at one output terminal on a transition from the one signal to the other signal from the detection circuitry (appliance turned on) and produces a pulse at another output terminal on a transition from the other signal to the one signal from the detection circuitry (appliance turned off).