Abstract: A portable biofeedback device for monitoring electric signals produced by muscle activity is disclosed. Electrodes attached to the skin of the person being monitored couple muscle signals to a preamplifier which amplifies the signal and does preliminary filtering of unwanted frequency components in this signal. Further high and low pass filtering and amplification is then performed such that only signals in a certain frequency range are amplified. Sensitivity control is added to enable the level of detected muscle activity to be selectively set. Both visual and audio feedback is generated from the filtered and amplified signal for use by the person being monitored. The visual feedback includes easy to read visual indicators, including an overrange indicator and underrange indicator, for displaying the varying levels of muscle activity.

Abstract: A pressure transducer comprised of a piezoresistance bridge on a semiconductor chip is employed as a pressure sensor in musical instruments having an air column through which pressure variations pass in producing sounds, such as in wind instruments and drums. A noiseless voltage preamplifier couples the transducer to a power preamplifier the output of which may then be amplified in a conventional audio amplifier. In the case of a wind instrument, the transducer is mounted between the cup or reed of the mouthpiece and the first key or finger hole, or in the air column in a direction opposite the first key or finger hole in the case of a transverse flute or similar reedless woodwind instrument for direct communication with the air column of the instrument.

Abstract: A system for suppressing positive feedback in acoustical-electrical devices having acoustic or electric feedback paths or a combination of both. Electrical signals from a microphone are transmitted through a sampling switch to a signal storage device. The transfer rate and duration are controlled by a pulse generator driven by an oscillator to time domain process the signals. The discrete signals output from the signal storage device are smoothed by a low pass filter and used to drive follow on circuitry, e.g., a speaker. A plurality of switches, signal storage devices, oscillators and pulse generators can be arranged in serial or parallel to provide various processing combinations. Several embodiments of the system are employed in a bidirectional telephone unit having separate incoming and outgoing signal channels to enable full duplex mode operation.