The VoiBridge is a VoIP to GSM Gateway supporting up to 4 SIMs for 4 simultaneous calls

Topex VoiBridge is a VoIP to GSM/UMTS small capacity gateway. Its main function is to interconnect VoIP networks with mobile networks. With Topex VoiBridge you make significant savings on calls from IP to GSM networks and backwards. 
  
Main Features
 
Up to 4 GSM Channels
H323 and SIP supported
Advanced incoming  call routing based on Caller- ID
Advanced call-routing of outgoing calls
SIM Server Ready
Advanced security with integrated firewall
VoIP to GSM/UMTS gateway
Interconnection with IP-PBXs based on SIP and H323
Advanced call-routing engine
Mobility Extension
Compatible with Asterisk 

Benefits 

Supports up to 4 cellular operators
No need to add any other gateway
Simple integration with VoIP networks
Least Cost Routing
Fast return of investment

Solutions

IPBX connection for GSM Network Calls
International Mobile Network Support 

 VoiBridge VoIP GSM Gateway Datasheet