SK 8 Voice Series (8-8,8-32) SK 8 Series VoIP Gateway is an 8-channel GSM VoIP Gateway used to smoothly transit between mobile and VoIP networks for transmission of voice and SMS. 1 channel supports 4-8 ports SIM Cards switching, which allows a great performance for cost saving. Integrated GSM connectivity and SIP protocol compatible with mainstream VoIP platforms, it is suitable for enterprises, multi-site organizations, call terminators and areas with limited landline like rural area to cut down telephone costs and enable easy & efficient communications.