The HT503 is a hybrid Analog Telephone Adapter (ATA) and VoIP Router. It features both an FXS (analog telephone) port and an FXO (PSTN) port so you can have backup lifeline support using a PSTN line in the case of a power outage. It also integrates 2 10/100 RJ45 ports with an integrated high performance NAT router..
The HT503 is an analog telephone adapter featuring 1 analog telephone FXS port and 1 PSTN line FXO port. The integration of a FXO and FXS port enables remote call origination and termination to and from the PSTN line, known as “hop-on and hop-off” calling. The 1 FXS port allows for extension of a VoIP service to 1 analog phone. In addition to being SIP compliant, the product features support for up to 2 SIP account profiles, excellent voice quality and advanced telephony features