Telefonaktiebolaget Lm Ericsson (publ)

Infineon Technologies Ag

Lantiq Deutschland Gmbh

Torbjorn Ivar Randahl

Stefan Barkaro

Andreas Wiesbauer

Lars Karlsson

Allan Olson

Bo Bokinge

Carl-Mikael Johansson

Sven Wiklund

Berndt Wallin

In a line driver/receiver circuit where the line driver is connected with its output terminals to a load for supplying a transmit signal thereto and where the receiver is connected with its input terminals to the load for simultaneously receiving a receive signal therefrom, the transmit signal on the input terminals of the receiver is canceled by connecting the output terminals of the line driver to the load via equal complex sense impedances of an impedance value that is much smaller than the impedance value of the load impedance to match the load impedance, connecting the input terminals of the receiver to the load via equal first resistors and to respective output terminal of the line driver via equal second resistors, and providing transconductance amplifiers to sense the voltage across the sense impedances and supply corresponding currents to respective input terminal of the line driver.

Echo canceling arrangement

A class D-amplifier which amplifies an input signal applied to an signal input of said amplifier () to generate an amplified signal output by an signal output () of said amplifier comprising a comparator () which compares the applied input signal with a switch signal to generate a pulse width modulated signal; a driving unit () which amplifies the pulse width modulated signal to generate the amplified output signal; and a feedback circuit which generates the self oscillating switch signal for the comparator ().

Class D-amplifier

In a transmitter/receiver for bidirectional communication with a transmission medium, the transmitter comprises an amplifier having an input terminal for signals to be transmitted, an output stage with output terminals coupled via resistors to the transmission medium, and a negative feedback circuit connected with its input terminals to the output terminals and with its output terminal to the input terminal of the amplifier. The receiver is connected with first input terminals to the output terminals of the output stage. A current mirror is connected with its input terminal to the input terminal of the amplifier output stage and with its output terminals via resistors across a load. The load is connected across second input terminals of the receiver. The receiver is adapted to extract signals received from the transmission medium by subtracting voltages between said second input terminals from voltages between said first input terminals.

Transmitter/receiver for bidirectional communications

In generating a ringing signal of predetermined frequency and shape between the A- and B-wires to a subscriber's station in a telephone network, the ringing signal is directly injected in or superposed on the DC-levels of the wires. A voltage difference converting device converts any voltage difference between the A- and B-wires into a first current. A signal generating device generates a first voltage of the frequency and shape of the ringing signal to be generated, and a signal converting device then converts the first voltage into a second current. In a summation node the first current is subtracted from the second current to obtain a third current and this current is converted by passing it through a resistor to a second voltage. The second voltage is buffered and is again converted to a fourth current by applying the voltage to resistor. This fourth current is amplified by current amplifiers circuits comprising operational amplifiers, and is then supplied to the A-wire and drawn from the B-wire.

Method and apparatus for generating a ringing signal

A method and an apparatus for off-hook detection in a subscriber line interface circuit responds to a ringing signal which preferably lacks a DC component. A signal is generated that is a function of the line current through the subscriber line, and the time at which the signal exceeds a predetermined current value is measured. The measured time is compared with a predetermined time value, and an off-hook indication is produced in a processor depending on the comparison.

Method for off-hook detection during ringing and the use of a subscriber

To generate a ringing signal by means of a subscriber line interface circuit having two final stages, each for supplying an individual subscriber line wire, one of the subscriber line wires is connected to one of the input terminals of an operational amplifier, the other input terminal of which being connected to the interconnecting point between two series connected resistors having the same resistance. The output terminal of the operational amplifier is connected, via a first resistor, to a current input terminal of the subscriber line interface circuit for generating a first current. A signal generator, via a second resistor, is also connected to said current input terminal for generating a second current. The final stages of the subscriber line interface circuit are supplied with current from current input terminal to drive the final stages to generate the ringing signal.

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Nacka, Sweden

Torbjorn Ivar Randahl