The HT503 is an analog telephone adapter featuring 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
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.

Grandstream HandyTone HT-503 Key Features:

1 FXS telephone port (RJ11), 1 FXO PSTN line port (RJ11) with power-outage life line support
Up to 2 SIP account profiles, SIP over TCP/TLS, SRTP
Dual 10/100 Mbps network ports (RJ45) with integrated high performance NAT router
Status LED for power, telephone, PSTN line, network, and message waiting indication
Advanced telephony features
Comprehensive voice codecs
Secure and automated provisioning using HTTP/HTTPS/Telnet/TFTP
Symmetric and asymmetric voice codec/RTP in any call sessions
T.38 Fax
SIP over TCP/TLS
IP connectivity for any phone and fax
Hop-on/Hop-off calling
Web management for easy configuration and installation
Offers traditional and advanced telephony features
Portable and compact for use at home or on the road

Grandstream HandyTone HT-503 Technical Specification

Telephone Interfaces
1 FXS port (RJ11)
1 FXO PTSN line port (RJ11) with lifeline support
Network Interfaces
Two 10M/100Mbps ports (RJ-45) integrated NAT router and auto-detection and support for either straight through or crossover cables
LED Indicators
Power, WAN, LAN, PHONE1 and LINE
Telephony Features
Caller ID display or block
Call waiting with caller ID
Flash, blind or attend call transfer
Hold