Patent ID: 7239628

Claim:
A network interface device, comprising: a first interface operable to receive a signal from a local loop circuit, the signal comprising power and packetized information; a power extractor operable to extract the power from the signal; a transceiver powered by the power extractor and operable to extract the information from the signal; a second interface operable to communicate the information to a user device; a ring generator operable to produce a ring signal for the user device, the ring generator comprising: a pulse modulator operable to generate a digital output signal in response to an input signal; a first output transistor operable to produce a first output voltage for a first duration determined based on an amplitude of the input signal; a second output transistor operable to produce a second output voltage for a second duration determined based on the amplitude of the input signal; a switch operable to switch between the first output transistor and the second output transistor in response to a zero crossing in the input signal; and a low-pass filter operable to convert output of the output transistors into an analog signal; an an automatic gain controller operable to: monitor a power level of the analog signal; and adjust an amplification level of the digital output signal based on the power level of the analog signal.