Abstract: A unidirectional microphone windscreen which includes portions formed of compressed foam and uncompressed foam located on opposite sides of the capsule to enhance directivity of the microphone.

Abstract: A bridge amplifier having paired high and low output stages in which a main amplifier receiving an input signal drives the high output stages and a balancing amplifier drives the low of the output stages. A junction temperature simulation circuit extends between the main amplifier and the low output stages in which the temperatures of the low output stages are sensed to produce an arresting of the main amplifier drive to the high output stages and thereby simultaneously control the balancing amplifier and its drive to the low output stages.

Abstract: A programmable signal generator which utilizes an eight bit microprocessor to generate a sixteen bit signal. Information is passed from an eight bit processor having a sixteen bit address register into one or more latches to produce a sixteen bit digital signal. The generator may be utilized in a time delay spectrometer to produce digital signals in quadrature form which are analyzed by the system microprocessor.

Abstract: A thermal protection circuit for the die of a transistor having a heat sink in which a signal proportional to the dissipative input current and a signal proportional to the dissipative applied voltage of the transistor are multiplied to produce a signal representative of the applied power to the transistor. This representative applied power signal is transformed into a simulated differential in temperature between the die of the transistor and its heat sink. Simultaneously, the temperature of the heat sink is determined and this temperature is added to the simulated differential in temperature between the die of the transistor and the heat sink to determine a sensed die temperature. A control responsive to this sensed die temperature reduces the applied power to the transistor.

Abstract: In a low-level audio preamplifier circuit having complementary connected PNP and NPN bipolar transistors cascode coupled to other complementary PNP and NPN bipolar transistors in receiving the audio input from a low-level transducer in which induced distortion from externally generated radio frequence energy is cancelled.

Abstract: In a low level audio preamplifier circuit having complementary connected PNP and NPN bipolar transistors for receiving the audio input from a low level transducer such as a tape head, in which induced distortion from externally generated radio frequency energy is cancelled with minimal loss of audio fidelity.