HT-544 4 FXS with 4 PSTN Bypass VoIP Gateway
The HT-544 is designed as a compact-size, high-performance and low-cost Analog Terminal Adaptor (FXS Gateway). It comes with 4 FXS ports to connect traditional analog phone or PBX trunk lines for VoIP communications, also has 4 PSTN line bypass. With easy installation and configuration, this gateway also supports 2 mostly used open VoIP standards (SIP and H.323), which makes it work seamlessly with soft switches or IP PBXs made by various vendors.
Offering high-quality voice, flexible networking and rich functions, it is an ideally low-cost solution for small and medium enterprises where multiple VoIP lines are required.

HT-544 4 FXS with 4 PSTN Bypass VoIP Gateway Key Features
Open Standard VoIP Protocols (ITU H.323 V4 and IETF SIP V2)
Two 10/100 Ethernet for WAN/LAN connections
Peer-to-Peer IP Calls
Speech quality ensured by QoS at the Ethernet and IP layers and comprehensive jitter buffer
Line Echo Cancellation
VLAN and QoS support
NAT Transversal and Router functions
Voice prompts, HTTP web, Auto Provision support for configuration and updates
Highly stable embedded Linux operating system in high performance ARM 9 Processor

HT-544 4 FXS with 4 PSTN Bypass VoIP Gateway Basic Features
Four RJ-11 FXS ports for traditional phone set or PBX's trunk line
Four RJ-11 ports for connection to PSTN line (Bypass function only)
LEDs for Power, Ready, Status, WAN, PC, FXS
Call Forward, Call Hold, Call Transfer
Dial Plan
Caller ID

HT-544 4 FXS with 4 PSTN Bypass VoIP Gateway Enhanced Features
Dynamic selection of codec
Advanced jitter buffer
Automatic traversal of NAT and firewall
VLAN/Qos
Router
Echo cancellation for Speakerphone
Comfort Noise Generation (CNG)
Voice Activity Detection (VAD)
Auto provisioning (requires auto provisioning server)
On line firmware upgrade
Multi-language support: English and Chinese

HT-544 4 FXS with 4 PSTN Bypass VoIP Gateway Supported Standards
ITU: H.323 V4, H.225, H.235, H.245, H.450
RFC 1889 - RTP/RTCP
RFC 2327- SDP
RFC 2833 - RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals
RFC 2976 - SIP INFO Method
RFC 3261 - SIP
RFC 3264 - Offer/Answer model with SDP
RFC 3515 - SIP REFER Method
RFC 3842 - A Message Summary and Message Waiting Indicator
RFC 3489 - Simple traversal of User Datagram Protocol (UDP) through Network Address Translators (NATs)
RFC 3891 - SIP "Replaces" Header
RFC 3892 - SIP Referred-By Mechanism
draft-ietf-sipping-cc-transfer-04- Session Initiation Protocol Call Control - Transfer
Codec: G.711 (A/μ law), G.729A/B, G.723.1
DTMF: RFC 2833, In-band DTMF, SIP INFO