Patent ID: 6947478

Claim:
An analog echo filter for an echo damping path of a modem, which is located between a transmit path and a receive path, in which case the modem can be supplied with an analog transmit signal, which is transmitted in full-duplex via a transmission line, via the transmit path, with the modem having an analog hybrid circuit for separating and combining the transmit signal and a received signal which can be output via the receive path, and having an active analog filter, whose transfer function is adjustable, wherein a passive analog input filter is provided for input balancing of the echo damping path and for adjusting a terminating impedance for the analog hybrid circuit; the transfer function of the active analog filter can be switched between a first-order transfer function and a second-order transfer function; the active analog filter has three operational amplifiers, which are connected in series; and the second operational amplifier in the series circuit can be bridged by switches in order to switch the active analog filter from a second-order transfer function to a first-order transfer function.