Patent ID: 8045702

Claim:
An apparatus for providing an interface between a transmission line, an input port, and an output port, the apparatus comprising: a ratio converter for producing a transmitted signal on the transmission line in response to an input signal arriving on the input port, and for producing a first signal in response to a received signal arriving on the transmission line, wherein the first signal includes an echo of the input signal; a first filter for filtering the input signal to produce a second signal; a second filter for filtering the input signal to produce a third signal, the second filter being an active filter that can be selectively turned off by a control signal; an amplifier circuit for summing and amplifying the first, second and third signals that form a fourth signal at an input to the amplifier circuit to produce a fifth signal at an output of the amplifier circuit; a first circuit for monitoring a processed version of an output signal provided from the output port to estimate a magnitude of a residual echo of the input signal in the output signal, and for generating the control signal to selectively turn the second filter on or off depending on the estimated magnitude of the residual echo; and a third filter coupled between the input port and the output port, the third filter for generating a sixth signal in response to the input signal, wherein the fifth and sixth signals combine to form the output signal at the output port.