Number of GSM channels (Max): 4 Network type: 850/900/1800/1900MHz Protocol: SIP (RFC3261), IAX2 Transport Protocol: UDP, TCP, TLS, SRTP DTMF: RFC2833, SIP INFO, In-band Codec: G.711 a/u-law, G.722, G.726, G.729a, GSM, ADPCM, Speex Echo Cancellation: ITU-T G.168 LEC LAN: 1 (10/100Mbps) Network: Static IP, DHCP Client, Firewall, VLAN, DDNS, QoS, OpenVPN NAT Traversal: Static NAT, STUN Size: 213x160x44mm Power Supply: AC 100-240V 50/60Hz 0.5A MAX Operation Range: 0 to 50C, 32 to 122 F Storage Range: -20 to 65C, 4 to 149 F Humidity: 10-90% non-condensing