An improved data access arrangement device for use in full-duplex two-wire
communication systems having a transmission impedance characteristic. The
DAA includes a transmit amplifier and a receive amplifier adapted for
connection to a two-wire line, a codec connected to the transmit
amplifier for generating a transmit signal, a summation device connected
to the receive amplifier, an echo cancellation path including a variable
gain amplifier, where the path extends between the codec and the
summation device, and wherein the variable gain amplifier is adjusted in
accordance with the transmission impedance characteristic. The variable
gain amplifier may include a gain register that is programmed by a
microprocessor, or may have the gain set by user-configurable switches.
The summation device is preferably an operational amplifier.