Telefonaktiebolaget Lm Ericsson (publ)

Lantiq Deutschland Gmbh

Stefan Barkaro

Torbjorn Ivar Randahl

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

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 buck boost switching regulator includes a buck switch and a boost switch controlled by a first and second comparator, respectively. The first comparator generates a duty cycle control signal for the buck switch in response to the difference between the regulator output voltage and a control voltage corresponding to a desired regulator output voltage. The second comparator generates a duty cycle control signal for the boost switch in response to a supply voltage.

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Solna, Sweden

Stefan Barkaro