Performance and features
    Support SIP protocol
    Support Bridge and Router(NAT&NAPT) models.
    TCP/UDP/IP, ICMP, HTTP, DHCP Client (WAN Interface), DHCP Server(LAN
    Interface), DNS Client, DNS Relay, SNTP, PPPoE, FTP, TFTP.
    Voice Codecs: G.711(A-law/U-law), G.723.1, G.729A/B
    Redundancy SIP server (or Gate Keeper): Can auto swap address between two
    servers address.
    NAT penetration: STUN client, AVS and Citron etc. Can modify SIP register port,
    HTTP server port, Telnet server port and RTP port. 
    Support two SIP server synchronously: Can register two different SIP
    server, and can make a call by either proxy.
    Support standard voice features such as numeric Caller ID Display, Call
    Waiting, Hold, Transfer, Do-Not-disturb, Forward, in-band and out-of-band
    DTMF, Hotline (off hook autodial), ban outgoing.
    Support standard encryption and authentication (DIGEST using MD5, MD5-
    sess).
    Support Silence Suppression, VAD (Voice Activity Detection), CNG (Comfort
    Noise Generation), Line Echo Cancellation (G.168), and AGC (Automatic Gain
    Control).
    Provide easy configuration thru manual operation (Web interface and Telnet)
    or automated centralized configuration file via TFTP or HTTP.
    Support firmware upgrade via TFTP/FTP and HTTP.
    Support syslog, can send event of gateway to syslog server.
• Main technical index
    Main CHIP:175 MHz/227 MIPS CPU
    Data storage:128Mbits SDRAM
    Program memory: 16Mbit Flash memory
    Application Network environment: Two 10/100Mbps Fast Ethernet MAC
    Power loss:4.5W(max)
    Power adapter: input AC100-240V,output DC 12V 1A
    Employing condition:
    Ambience temperature 0-40??32-104°F?
    Relative humidity 10-95%
    Atmosphere pressure 86-106Kpa
    Overall size:114x154x34mm (L x W x H)