Specification :

Integrating with IP-PBX like asterisk, 3CX
Interconnection or extension for PABX
VoIP service like calling card, call termination
VoIP gateway also can provides following functions
PBX function: lines hunting, IVR DID, caller ID, hotline, call transfer, call waiting
Adjustable line gain, automatic detection for busy tone, caller ID, DTMF, automatic dialing
RS gateway supports SIP and MCGP protocols
They can provide PBX functions such as hunting group, second stage dialing, internal communications, caller ID ( FSK/ DTMF) , call transfer, call waiting, call hold, call barring, caller ID restriction hotline, corporate CRBT and more
FXO related functions such as PSTN fail-over, gain control, busy tone detection, voice prompt in inbound calls, polarity reversal detection
Media stream processing functions such as RTP redundancy, packet loss compensation, G.711/ G.729A/ G.723.1/ iLBC/ GSM voice codec, echo cancellation