Abstract: To establish communication between a host and a client, electromagnetic field is generated across coils disposed in the devices. The magnetic field generated across the coil disposed in the host is used to power the client and to transfer data to the client. The data received by the client may, in turn, be used to configure the client. To receive data from the client, the coil disposed in the host is placed in a quiescent data recovery mode. The data to be transmitted from the client to the host generates variations in magnetic field formed across the client's coil. These variation, in turn, form variations in the magnetic field across the coil disposed in the host, and are subsequently decoded by the host to detect the data transmitted from the client. Supporting circuitry in both the host and client convert the electromagnetic variations into a stream of bits.

Abstract: An electrically active sound wave attenuation apparatus mounted in an upright, free-standing housing for eliminating unwanted reflected waves in a room. The housing is intended to be placed in a location where undesired wave patterns, such as standing waves, are formed in order to offset or cancel such conditions. These conditions are offset by generating an acoustic signal which is the inverse of pressure waves at a particular location. The pressure waves are sensed by a module, including a microphone which generates a corresponding electrical signal. This signal is sent to an electrical circuit where an inverse signal is created which is then transmitted to a loudspeaker. The loudspeaker output is directed toward the location where the standing waves would be formed. The loudspeaker output nulls local acoustic waves so that no standing waves are formed. The housing may incorporate two acoustically isolated modules with resonance attenuating qualities, one at each end of the structure.

Abstract: A high fidelity audio amplifier of the push-pull complementary symmetry type, featuring a feedback circuit with a bias sensing element connected to the output terminals of the output transistors. The feedback circuit includes a photoemitting element in optical communication with a photoconductive element which determines the relative voltage difference of the input terminals of the complementary symmetry output transistors.

Abstract: A transistor amplifier in which collector to emitter voltages and currents are kept constant, particularly in the power output stages of the amplifying devices for minimizing distortion due to changes in the transistor beta, the essential form of distortion in amplifiers. High fidelity low power output current from a cascoded transistor amplifier is fed through a load to a second, high power, amplifier having constant current and less than unity gain, with an output summed with the output of the first amplifier such that the output of the first low power amplifier is the signal bearing portion and the output of the second amplifier serves as a current bootstrap, increasing the effective impedance of the load as seen by the first amplifier.

Abstract: A transistor audio amplifier of the Class AB complementary symmetry type is biased with a new bias circuit to keep both transistors on during all normal signal conditions. The bias circuit includes a pair of series connected V.sub.BE Multipliers with an interconnection between the two multipliers receiving signal feedback from the amplifier output such that the Multipliers can bias both complementary transistors on for all normal signal operating conditions.