Method and apparatus for ringing

1. A method for ring-trip detection in a line card, comprising:

using an analog-to-digital converter for processing voice signals;

receiving a ringing control signal;

transmitting a ringing signal to a subscriber line in response to the ringing control signal;

receiving a portion of the ringing signal from the subscriber line;

converting the portion of the ringing signal to a digital signal using the analog-to-digital converter;

transmitting the converted digital signal to a ring detection unit and then to a digital interface, the digital interface being adapted to transmit a ring control signal to a ring generator;

generating a ring-trip indication at the ring generator in response to receiving the ring control signal;

transmitting the ring-trip indication through a switch to a digital-to-analog converter, the digital-to-analog converter being adapted to convert the ring-trip indication to an analog signal; and

providing the converted, analog ring-trip indication.

2. The method of claim 1 , wherein the ringing signal comprises an AC signal.

3. The method of claim 1 , further including terminating the ringing signal in response to the ring-trip indication.

4. A method, comprising:

processing a voice signal in a low-current mode of a line card, the line card having an analog-to-digital converter for converting the voice signal to a digital signal;

receiving a ringing control signal;

switching to a high-current mode of the line card in response to the ringing control signal;

ringing a telephonic device in response to switching to the high-current mode of the line card;

converting the portion of the ringing signal to a digital signal using the analog-to-digital converter;

transmitting the converted digital signal to a ring detection unit and then to a digital interface, the digital interface being adapted to transmit a ring control signal to a ring generator;

generating a ring-trip indication at the ring generator in response to receiving the ring control signal;

transmitting the ring-trip indication through a switch to a digital-to-analog converter, the digital-to-analog converter being adapted to convert the ring-trip indication to an analog signal; and

providing the ring-trip indication in the high-current mode.

5. The method of claim 4 , wherein the ringing signal comprises an AC signal.

6. The method of claim 4 , further including terminating the ringing signal in response to the ring-trip indication.

7. An apparatus, comprising:

first circuitry capable of processing a voice signal, the first circuitry including an analog-to-digital converter for processing the voice signal;

a ringing generator capable providing a ringing signal to a subscriber line in response to receiving a ringing control signal;

second circuitry capable of delivering the portion of the ringing signal to the analog-to-digital converter of the first circuitry, wherein the analog-to-digital converter converts the portion of the ringing signal to a digital signal;

a digital interface adapted to provide the ringing control signal to the ringing generator;

ring-trip detection logic capable of providing a ring-trip indication in response to the digital signal; and

a digital-to-analog converter adapted to convert the provided ringing signal to an analog signal for the subscriber line.

8. The apparatus of claim 7 , further including third circuitry capable of terminating the ringing signal in response to the ring-trip indication.

9. The apparatus of claim 7 , wherein the ringing signal comprises an AC signal.

10. The apparatus of claim 7 , wherein the ring-trip detection logic provides a ring-trip indication based on a power of the digital signal over a selected interval.

11. A line card, comprising:

a subscriber line interface circuit capable of:

receiving a voice signal from the subscriber line;

delivering a ringing signal to the subscriber line; and

receiving at least a portion of the transmitted signal from the subscriber line; and

logic capable of:

processing the voice signal using an analog-to-digital converter;

delivering the portion of the ringing signal to the analog-to-digital converter for converting the portion of the ringing signal to a digital signal;

transmitting the converted digital signal to a ring detection unit and then to a digital interface, the digital interface being adapted to transmit a ring control signal to a ring generator;

generating a ring-trip indication at the ring generator in response to receiving the ring control signal;

transmitting the ring-trip indication through a switch to a digital-to-analog converter, the digital-to-analog converter being adapted to convert the ring-trip indication to an analog signal; and

providing the converted, analog ring-trip indication.

12. The line card of claim 11 , wherein the subscriber line integrated circuit is a voltage subscriber line interface circuit.

13. The line card of claim 12 , wherein the subscriber line interface circuit is capable of receiving a data signal in a frequency band above voice signals.

14. The line card of claim 12 , wherein the logic provides a ring-trip indication based on a power of the digital signal over a selected interval.

15. The line card of claim 12 , wherein the ringing signal is an AC signal.

16. An apparatus for ring-trip detection, the apparatus having an analog-to-digital converter for processing voice signals, the apparatus comprising:

means for receiving a ringing control signal;

means for transmitting a ringing signal to a subscriber line in response to the ringing control signal;

means for receiving a portion of the ringing signal from the subscriber line;

means for converting the portion of the ringing signal to a digital signal using the analog-to-digital converter;

means for transmitting the converted digital signal to a ring detection unit and then to a digital interface, the digital interface being adapted to transmit a ring control signal to a ring generator;

means for generating a ring-trip indication at the ring generator in response to receiving the ring control signal;

means for transmitting the ring-trip indication through a switch to a digital-to-analog converter, the digital-to-analog converter being adapted to convert the ring-trip indication to an analog signal; and

means for providing the converted, analog ring-trip indication.

17. A non-transitory, computer readable storage device adapted to store program instructions that, when executed by a processing device, perform a method for ring-trip detection in a line card, comprising:

using an analog-to-digital converter for processing voice signals;

receiving a ringing control signal;

transmitting a ringing signal to a subscriber line in response to the ringing control signal;

receiving a portion of the ringing signal from the subscriber line;

converting the portion of the ringing signal to a digital signal using the analog-to-digital converter;

transmitting the converted digital signal to a ring detection unit and then to a digital interface, the digital interface being adapted to transmit a ring control signal to a ring generator;

generating a ring-trip indication at the ring generator in response to receiving the ring control signal;

transmitting the ring-trip indication through a switch to a digital-to-analog converter, the digital-to-analog converter being adapted to convert the ring-trip indication to an analog signal; and

providing the converted, analog ring-trip indication.

18. A non-transitory, computer readable storage device adapted to store program instructions that, when executed by a processing device, perform a method for ring-trip detection in a line card, as set forth in claim 17 , further comprising:

terminating the ringing signal in response to the ring-trip indication.