Abstract: A high fidelity hearing aid amplifier is operable at a very low battery voltage and includes a single integrated circuit chip which provides a variable gain amplifier and gain control circuitry operative at low signal levels to enhance gain at higher frequencies relative to gain at lower frequencies, such circuitry including a logarithmic rectifier arrangement and a peak detector in a compression ratio control circuit. Operation at a low battery voltage is enhanced through a compression ratio control circuit which provides a level shift between an AC output of the logarithmic rectifier arrangement and the peak detector. Current mirrors are provided to obtained balanced and stable operation, and an arrangement is provided for manual control by a user to obtain an optimum response characteristic.

Abstract: A current controlled variable attenuator circuit using a current controlled resistor is disclosed. In paticular, the current controlled resistor and attenuator are particularly suited for use in hearing aids due to the resistor's and attenuator's easy implementation in bipolar integrated circuits. The current controlled resistor and attenuator also has wide application to other circuitry requiring controlled variable resistance elements having a broader linear response than previously available. The current controlled resistor consists of transistors having inherent non-linear characteristics which can be linearized by adding appropriate compensation circuitry.

Abstract: A system for detecting and transmitting body electrical signals in the presence of ambient electrical interference that uses a transmiter circuit including an amplifier coupled to and in close proximity to two or more body electrodes, a light pulse generator that receives its input from that amplifier and provides a pulse-duration-modulated series of light pulses, and a remote receiver including a transducer which demodulates the transmitted light pulses into electrical pulses of corresponding duration and frequency and a demodulator which accepts those electrical pulses and produces an amplified replica of the original signal developed between the body electrodes, thereby effectively providing complete electrical isolation of the electrode amplifier from the remaining bioelectrical signal analysis equipment.

Abstract: A dual drum skimmer is provided for the removal and recovery of oil floating on water. The skimmer includes two oil pick-up drums arranged along a common axis which pick up oil and deposit it in a collection trough. Oil deposited in the collection trough is directed to a reservoir trough arranged on the opposite side of the drums from the collection trough. The drums are formed as hollow, closed cylinders and, together with the reservoir trough, provide the total buoyancy necessary to float the skimmer. The skimmer is particularly effective in shallow and in trash laden water and can operate in water depths of as little as three inches.

Abstract: Response-modifying acoustic couplers are provided for use between an output port of a hearing aid unit and an earmold at the entrance to the ear of a wearer, including a passage and a chamber which respectively provide a high acoustic inertance and a high acoustic compliance to cooperate with other acoustic elements and to form an acoustic network producing a predetermined frequency response characteristic.

Abstract: A patch-like web of material adapted to be placed over skin tumors for aiding a physician in making an optimum size and shape incision when surgically removing the tumor. The web of material is provided with an opening having a predetermined size which correlates with the size of the tumor. Also included are delineation provisions for providing a pattern which prescribes the optimum size and shape for the particular incision.