Abstract: A voltage and speed sensitive solid state motor control starting circuit is a RPM voltage sensing circuit for controlling the starting circuit operation of an AC induction motor. The circuit effectively removes the start capacitor from the AC circuit at a predetermined RPM cutout voltage and reengages the start capacitor at a predetermined cut in voltage. The circuit may be installed on an AC induction motor to replace conventional mechanical switches that are used for removing start capacitors from the AC induction motor circuit. The circuit is more simplified and less complex than conventional mechanical switches, while being very efficient.

Abstract: A differential amplifier circuit comprised of two operational amplifiers for use as a differential output and differential input amplifier for any two-terminal impedance transfer function. The input impedance is very low between the two input terminals, yet it is very high between either input terminal and the common or ground terminal, thus giving this amplifier many of the desirable characteristics of a transformer-coupled amplifier. High common mode voltage rejection ratios can be achieved even when moderate differential imbalances exist in the input and feedback networks due to the unique balancing feature of the circuit.

Abstract: A seismic amplifier for use in marine seismic survey work involving the transmission of signals from remote signalling stations over cable pairs to signal processing equipment. These signalling stations are comprised of capacitive transducers. The seismic amplifier of the surveying system includes operational amplifiers electrically interconnected with a feedback circuit comprised of a balanced resistive-reactive network which is a lumped parameter equivalent circuit of the transmission line and capacitive transducer. The lumped parameter equivalent circuit used for feedback provides a flat, zero-phase shift overall response over the cable pair from the transducer to the output of a differential amplifier stage which is connected to the operational amplifier outputs to improve common mode rejection.