The HT813 is an analog telephone adapter that features 1 analog telephone FXS port and 1 PSTN line FXO port in order to offer backup lifeline support using a PSTN line . The integration of a FXO and FXS port enables this hybrid ATA to support remote calling to and from t he PSTN line. For added flexibility, the FXS port extends VoIP service to one analog device. Users can conve rt their analog technology to VoIP thanks to the HT813’s ultra-compact size, HD voice quality, advanced VoIP functionality, high-end security protection and multiple auto provisioning options. These advanced features also allow service providers to offer high quality IP service to customers looking to upgrade to VoIP.