Method for transmitting line signals via a line device, and transmission apparatus

1. A transmission apparatus, comprising:

a) a line device configured to transmit line signals at prescribed signal levels; and

b) a line driver device, comprising:

an amplifier unit configured to amplify the line signals such that said amplified line signals are driven onto the line device at the prescribed signal level,

a control unit configured to control an operating mode of the amplifier unit using an operating-mode control signal,

a determination unit configured to determine when a prescribed reference signal level is exceeded by a signal level of the line signals and to generate a control signal responsive to said determination,

the determination unit operably coupled to provide the control signal to the control unit, wherein the control unit is configured to use the operating-mode control signal to cause the amplifier unit to change to a different operating mode responsive to receiving the control signal,

wherein the line driver device is a subscriber line interface circuit, wherein the line driver device is arranged in the apparatus such that it is protected against overvoltages and overcurrents,

wherein the line driver device includes a mode control bus configured to supply an externally-generated mode control signal to the control unit, and

wherein the control unit is further configured to generate the operating-mode control signal based on the externally-generated mode control signal.

2. The apparatus as claimed in claim 1 , wherein the determination unit includes a detection unit configured to detect the signal level of the line signals.

3. The apparatus as claimed in claim 2 , wherein the determination unit further comprises a comparison unit configured to compare the detected signal level of the line signals with the prescribed reference signal level.

4. The apparatus as claimed in claim 2 , wherein the detection unit is configured to detect a potential difference which is present on the line device.

5. The apparatus as claimed in claim 2 , wherein the detection unit is configured to detect a current signal which corresponds to a current flowing in the line device.

6. A method for transmitting line signals via a line device operably connected to a subscriber line interface circuit, the subscriber line interface circuit including at least a control unit, an amplifier unit, a detection unit and a comparison unit, the method comprising:

a) controlling the amplifier unit by means of the control unit to operate in an operating mode using an operating-mode control signal;

b) amplifying by means of the amplifier the line signals to be transmitted to a prescribable signal level using the amplifier unit on the basis of the operating mode;

c) providing the line signals to be transmitted onto the line device;

d) detecting the signal level of the line signals by means of the detection unit;

e) automatically comparing the detected signal level of the line signals by means of the comparison unit with a reference signal level, said comparison being made against the reference signal level, the reference signal level comprising a reference current signal;

f) generating a control signal based on the comparing of the detected signal level of the line signals with the reference signal level, the control signal provided to the control unit;

g) automatically and selectively switching the amplifier unit by means of the operating-mode control signal to a safety operating mode based on results of the comparison;

h) supplying an externally-generated mode control signal to the control unit; and

i) generating the operating-mode control signal based on the externally generated mode control signal.

7. The method as claimed in claim 6 , wherein step f) further comprises switching the amplifier unit to the safety operating mode by turning off the amplifier unit.

8. The method as claimed in claim 6 , wherein step e) further comprises automatically comparing the detected signal level of the line signals with the reference signal level, the reference signal comprising a reference potential difference.

9. The method as claimed in claim 6 , wherein step d) further comprises detecting a potential difference which is present on the line device.

10. The method as claimed in claim 6 , wherein step d) further comprises detecting a current flowing in the line device.

11. The method as claimed in claim 6 , further comprising supplying a reference potential difference signal as the reference signal level for comparison.

12. The method as claimed in claim 6 , wherein: step e) further comprises using a comparison unit to compare the detected signal level of the line signals with a reference signal level; and step f) further comprises automatically and selectively switching the amplifier unit to a safety operating mode based on results of the comparison, by generating a control signal in the comparison unit if the detected signal level exceeds the reference signal level.