Lucent Technologies Inc.

At+t Corp.

Pro Tech Communications Inc.

David A Brown

James Edward West

Alan Dean Michel

Wayne Allen Weise

Bruce D Wycherley

Nasrin Hoque

Frank S Simone

Fred Remite, Jr

Hans K Keipert

A system that provides a means of effectively applying a mathematical substitution to the characteristic V/I equation for FET devices operating in the ohmic region that causes the non-linear (distortion producing) term to be cancelled thereby improving the realizable channel impedance linearity by orders of magnitude. The system comprised of a means to sum an isolated specific portion of the information signal applied to the FET with the Gate controlling voltage to produce a signal value that achieves the improved linearity result when applied to the FET Gate terminal.

Linearization of FET channel impedance for small signal applications

A distortion reduction system for an audio device having first and second power supply voltages, a driver circuit for amplifying an audio signal, and, a speaker for outputting the amplified audio signal, allows a speaker driver system to increase significantly its average acoustic output power without appreciably degrading the audio signal quality. The system performs this function independently of the power supply voltage value by detecting a voltage difference between instantaneous peak amplified audio signal value and each first and second power supply voltage values and, providing a first gain control signal to the driver circuit when the detected difference is greater than a predetermined trigger level value, and a second gain control signal to the driver circuit when the detected difference is less than the predetermined trigger level value. In this system, the first and second gain control signals operate to maximally maintain the amplified peak-to-peak audio signal values between power supply voltage limit values and prevent onset of audio signal distortion while maximizing the average RMS value.

Distortion reduction system

In an embodiment of the invention, a speaker/microphone peripheral includes a digital-signal-processor (DSP) based acoustic echo canceler and supports a plurality of modes of operation. One mode is a video/telecommunications mode. In this mode, when headphones are inserted or removed, the acoustic echo canceler is reset.

Intelligent acoustic systems peripheral

An accessory connector and adapted assembly (30) that utilizes a connection to the reference voltage line (19') of the interface (19) between a personal computer (10) and its keyboard or other accessory (14), thereby avoiding the need to provide an independent power supply circuit for peripheral devices and accessories such as a microphone (20), speakers or the like. The adapter assembly (30) is configured with a first interface (28) having, by way of illustrative example, a male connector portion (28A) dimensioned for insertion into the keyboard port or PS2 port (19) of a personal computer and a female connector portion (28B) dimensioned to accommodate the male termination (18) of a conventional keyboard cable (17). The adapter assembly further includes a second interface (26) for providing power to the one or more external peripheral devices. By way of illustrative example, the second interface may include one or more jacks, male or female, to accommodate the terminating connector of a cable associated with one or more audio speakers and/or a loudspeaker. As a further example, a first connector (26A) of second interface (26) will connect to an audio peripheral input (32) located at the rear of a processing unit (16) of the computer (10), and an accessory conductor plug 24 of a microphone (24) will connect to a second connector (26B).

Interface assembly for peripheral accessories

A rail-to-rail driver amplifier circuit that utilizes complementary output transistors to fully utilize the available power supply voltage. The circuit includes an input pre-amplifying circuit for receiving the audio signal and for receiving electrical energy from a power supply having a first rail at a positive potential and a second rail at a negative potential to produce a pre-amplified output signal. The circuit further includes a first output driver circuit having a voltage gain limited current amplifier coupled to the first rail and to a first output terminal of the input pre-amplifying circuit and a second output driver circuit having a voltage gain limited current amplifier coupled to the second rail and to a second output terminal of the input pre-amplifying circuit. The input pre-amplifying circuit is operable to supply the pre-amplified output signal to one of the output driver circuits when the input signal current exceeds a current threshold and to the other of the output driver circuits when the input signal current is below the current threshold. The complementary speaker driver output circuits are mirrored about the voltage appearing at a capacipacitance. This voltage will equal the value of the system signal ground which is usually midway between the positive and negative power supply rails (Vmid).

Stabilized rail-to-rail speaker driver circuit

A public facsimile machine is arranged so that it will only receive an incoming facsimile if the facsimile is preceded by a predetermined security code. In addition, the public facsimile machine is associated with an enhanced facsimile service so that the capabilities provided by such a service, for example, broadcasting a facsimile to a plurality of destinations, may be offered to a user of the public facsimile machine.

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Indianapolis, IN, United States of America

David A Brown