function 10/100base-t or wifi h.323, mgcp, h.248, tcp/ ip, udp, rtp/ rtcp, http, icmp, arp, dns, pppoe, dhcp, tftp/ ftp, telnet, snmp etc; advanced digital signal processing( dsp) hardware to insure high and clear voice quality, support the voice activity detection (vad) technology, comforting noise generation( cng) technology, silence compression, echo eliminator( g.168), can change compression arithmetic dynamically when network blocked. communicate mutually with other center equipments, gateways and terminals as well; itu- t g.711( a- law/ m- law), g.723.1, g.729 compression coding etc; standard services such as cli, caller id detection and generation etc; value-added services and applications such as call transfer, call wait, call hold etc; hand-free, redial, telephone record, volume adjustment; pass though nat, realize mutual communication in nat or between in and out of nat(telephone, iad, tmg); tos function, guarantee voice quality; add, intercept, modify prefix of phone number, abbreviation dial; reset system configuration through keyboard, snmp agent, web or telnet, support remote software upgrade.