Telefonaktiebolaget Lm Ericsson (publ)

Elisabeth Maria Larsson

Hans Oskar Eriksson

Henrik Helmer Hellberg

Carl-Henrik Jorgen Malmgren

In a subscriber line interface circuit, a device applies to a line, associated with the line interface circuit, a substantially constant line current of a first predetermined value for line voltages up to a first voltage having an absolute value which, by a predetermined amount, is lower than the supply voltage of the line interface circuit. For line voltages between the first voltage and a second voltage having an absolute value which, by a predetermined amount, is higher than the first voltage, a line current which is inversely proportional to the line voltage and of a value between said first predetermined value and a second predetermined, lower value is applied to the line. For line voltages between the second voltage and a third voltage having an absolute value which, by a predetermined amount, is higher than the second voltage, a substantially constant line current of the second predetermined value is applied to the line. For line currents of lower value than said second predetermined value, the line voltage is maintained substantially constant at the third voltage.

Subscriber line interface circuit

In a method and an arrangement for adapting, from a DC point of view, the signal input of a first circuit, lying at a first DC voltage, to the signal output of at least one second circuit, lying at a second DC voltage, the signal input terminal is connected to the respective signal output terminal of the respective second circuit via a respective first resistance, whereby first DC currents will be allowed to flow through the respective first resistance. The signal input is adapted to be virtually short-circuited to a source for the first DC voltage, which is of a predetermined value, separate from zero. The first circuit is adapted to internally generate a DC cancellation current and bring it to flow in the signal input. The signal input is to be connected to ground via a selectable, second resistance, whereby a second DC current will flow through the second resistance. This second resistance is to be selected in such a manner that the sum of the DC cancellation current, the first DC currents, and the second DC current, equals zero.

Method and an arrangement for adapting from a DC point of view a first circuit to at least one second circuit

Method and apparatus for determining the deviation of longitudinal

A protective circuit in a power amplifier is adapted, by limiting the maximum output current of the power amplifier and by quickly recharging compensating capacitors in the power amplifier, to limit the amount and duration of the power drain in the power amplifier upon over-excitation of the power amplifier.

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Bromma, Sweden

Elisabeth Maria Larsson