Abstract: A balanced hybrid circuit for compensating for transmission echo signal in a modem. The hybrid circuit includes transmission echo compensation circuits that approximate the echo signal effects of the line and line transformer, respectively, and produce a transmission echo signal replica. A sample of the transmission signal and the replica of the transmission echo are then subtracted from the signal received on the line to produce a received signal isolated from the transmission signal and the transmission echo signal.

Abstract: A driver for coupling a transceiver to a line, including a first amplifier having first and second inputs and a first output coupled to a first side of the line. The driver includes a second amplifier having a third input and a fourth input and a second output coupled to a second side of the line. The driver further includes a first voltage feedback resistor, connected between the first output and the second input, and a second voltage feedback resistor, substantially the same as the first voltage feedback resistor, connected between the second output and the fourth input. The driver also includes a series resistor, coupled between the first output and the second output; and a gain resistor connected between the second input and the fourth input. The driver further includes two substantially similar current feedback resistors, connected between the gain resistor and the series resistor.

Abstract: A line driver for coupling a data transceiver to a line, including a first amplifier having a first input and a second input and a first output coupled to a first side of the line, the first input being coupled to a first input terminal. The driver includes a second amplifier having a third input and a fourth input and a second output coupled to a second side of the line, the third input being coupled to a second input terminal. The driver further includes a first voltage feedback resistor, having a first voltage feedback resistance, connected between the first output and the second input, and a second voltage feedback resistor, having a resistance substantially equal to the first voltage feedback resistance, connected between the second output and the fourth input.

Abstract: A system and method is presented for reducing the power consumed by a line driver driving a signal to be transmitted through a communications media. The preferred method includes the steps of: (1) delaying the signal; (2) determining whether the signal has reached a predetermined threshold value; (3) increasing power supplied to the line driver in response to an indication from the determining step that the threshold has been reached; and (4) delivering the delayed signal to the line driver. The preferred system includes: (1) a digital signal processor; (2) a line driver; (3) a digital delay line disposed between the digital signal processor and the line driver; and (4) a power regulator disposed between the threshold detector and the line driver. The system and method, while applicable to many communications formats, is particularly applicable to communications methods transmitting signals having a relatively large dynamic range, such as xDSL communications techniques.

Abstract: A line driver for coupling a data transceiver to a line having a load impedance, having a transformer with a primary coil and a secondary coil with a turns ratio of N:1 therebetween. The line driver includes a shunt impedance set to a value equal to a predetermined function of N and of the load impedance, coupled between one end of the primary coil and ground. The line driver also includes a differential amplifier, having a first input coupled to be driven by a transmit circuit of the transceiver, and having an output coupled to drive the line through the secondary of the transformer, and having a second input shunted to ground through the shunt impedance and coupled to receive feedback from the output through the primary coil of the transformer.

Abstract: This invention relates to electronic equipment comprising microprocessors, and more specifically microprocessors employed within radio receiver circuits, incorporating on-chip memory (301, 302, 303) and which have the ability to operate in either a single chip or expanded mode. The single chip mode restricts microprocessor (300) operation to internal operation and thereby inhibits external addressing and locally generated noise whereas the expanded mode allows external addressing. A software program, comprised from modules of program code, is categorised into a first and a second category of routines. First category routines are related to equipment functions which are affected by generated noise to a higher degree and, when in operation, are stored in the internal memory (301, 302, 303). Second category routines are stored in a memory external to the microprocessor (201, 202) and are related to equipment functions which are affected by generated noise to a lesser degree.