A communication apparatus is used to interface signals with any one of a plurality of telephony networks having different impedances. The apparatus includes memory, a processor, a digital-to-analog (D/A) converter, and an interface port. Different sets of impedance control values are stored in the memory. The processor is configured to select one of the sets of impedance control values and to serially transmit the selected set of impedance control values during a communication session. The D/A converter is configured to receive the selected set of impedance control values from the processor and to transmit analog signals based on the selected set of impedance control values. The interface port is configured to interface signals with a communication connection of a telephony network. Based on the analog signals transmitted by the D/A converter, the interface port simulates an impedance such that the simulated impedance substantially matches an impedance of the telephony network as measured from the communication connection.