Method and Device for Checking a Subscriber Line

A method for checking a subscriber line with a first and a second electrical line, wherein each line is connected to an encoder/decoder via a subscriber line circuit, comprising:

• connecting the first line connected to ground;
• increasing a resistance of the second line;
• outputting from the encoder/decoder an audio signal to the first line;
• measuring 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 a second frequency-selective signal at a point at which the encoder/decoder is connected to the second line;
• and
• ascertaining an amplitude difference between the first and second frequency-selective signals.

A device for checking a subscriber line with a first and a second electrical line, comprising:

• a tone generator and a frequency-selective measuring unit arranged in an encoder/decoder, wherein first electrical line and the second electrical line are connected to the encoder/decoder via a subscriber line circuit, wherein the tone generator and the frequency-selective measuring unit are configured to be controlled sequentially depending on a first and a second configuration,
• wherein the first configuration is formed by virtue of a first connection of the first line to ground, by virtue of an increase in a resistance of the second line, by virtue of an output of an audio signal from the tone generator to the first line, and by virtue of a connection of the frequency-selective measuring unit to a point at which the encoder/decoder is connected to the first line, and
• wherein the second configuration is formed by virtue of a second connection of the second line to ground, by virtue of an increase in a resistance of the first line, by virtue of output of an audio signal from the tone generator to the second line, and by virtue of a connection of the frequency-selective measuring unit to a point at which the encoder/decoder is connected to the second line, and
• wherein the measuring unit comprises a differentiator.