User Guide
Grandstream Networks, Inc.  HT-502 User Manual  Page 8 of 31 
  Firmware 1.0.0.29  Last Updated: 01/2007 
TABLE3: HT–502 TECHNICAL SPECIFICATIONS 
HT–502 Analog Telephone Adaptor 
Telephone Interfaces 
2 FXS ports, 2 SIP accounts  
Network Interface 
Two (2) 10M/100 Mbps, RJ-45 
LED Indicators 
Power, WAN, LAN, PHONE1 and PHONE2 
Reset Button 
Factory Reset button. 
Voice over Packet 
Capabilities 
Voice Activity Detection (VAD) with CNG (comfort noise generation) and 
PLC (packet loss concealment), Dynamic Jitter Buffer, 
Modem detection & auto-switch to G.711, 
Packetized Voice Protocol Unit (supports RTP/RTCP and AAL2 protocol), 
G.168 compliant Echo Cancellation, LEC (line echo cancellation) with NLP 
Voice Compression  G.711 + Annex I (PLC), Annex II (VAD/CNG format) encoder and decoder, 
G.723.1A, G.726(ADPCM), G.729A/B/E, iLBC 
G.726 provides proprietary VAD, CNG, and signal power estimation 
Voice Play Out unit (reordering, fixed and adaptive jitter buffer, clock 
synchronization), AGC (automatic gain control), 
Status output, Decoder controlling via voice packet header 
DHCP Server/Client 
Yes, NAT Router or Switched Mode 
Fax over IP  T.38 compliant Group 3 Fax Relay up to 14.4kpbs and auto-switch to 
G.711 for Fax Pass-through (pending), Fax Datapump V.17, V.19, V.27ter, 
V.29 for T.38 fax relay 
QoS 
Diffserve, TOS, 802.1 P/Q VLAN tagging 
IP Transport 
RTP/RTCP 
DTMF Method  Flexible DTMF transmission method, user interface of In-audio, RFC2833, 
and/or SIP Info 
IP Signaling 
SIP (RFC 3261) 
Provisioning 
TFTP, HTTP, HTTPS (pending) 
Control 
TLS/SIPS 
Management  Syslog support, HTTPS and telnet (pending), remote management using 
Web browser 
Support Layer 2 (802.1Q, VLAN, 802.1p) and Layer 3 QoS (Tos, DiffSery, 
MPLS) 
Auto/manual provisioning system 
Power 
Output: 12VDC / Input: 100–240 VAC/50-60 Hz 
Environmental 
Operational: 32
o
–104
o
F or 0
o
–40
o
C 
Storage: 10
o
–130
o
 F / Humidity: 10–90% Non-condensing 
Dimensions 
(H x W x D) 
Short and long haul 
REN3: Up to150 ft on 24 AWG line 
Call Handling 
Features 
Caller ID display or block, Call waiting caller ID, Call waiting/flash, Call 
transfer, hold, forward, mute, 3-way conferencing 
Caller ID 
Bellcore Type 1 & 2, ETSI, BT, NTT, and DTMF-based CID 
Polarity Reversal / 
Wink 
Yes 
EMC  EN55022/EN55024 and FCC part15 Class B 
Safety 
UL 










