Patent ID: 8509421

Claim:
A method for checking a subscriber line circuit with a first and a second electrical line, wherein each line is connected to an encoder/decoder of a codec via a subscriber line circuit, the codec including a frequency selective measuring unit, the method comprising: connecting the first line to ground; increasing a resistance of the second line; outputting from the encoder/decoder an audio signal to the first line; measuring, via the measuring unit, a first frequency-selective signal at a point at which the encoder/decoder is connected to the first line; connecting the second line to ground; increasing a resistance of the first line; outputting from the encoder/decoder a further audio signal to the second line; measuring, via the measuring unit, a second frequency-selective signal at a point at which the encoder/decoder is connected to the second line; ascertaining, via the measuring unit, an amplitude difference between the measured first and second frequency-selective signals; and ascertaining an asymmetry at inputs of the subscriber line, via the measuring unit based on the amplitude difference circuit.