Concerning practical implementation, the VoIP gateways have proven to be the best. Many companies are successfully using the IP telephony thanks to its two main characteristics
Decrease in international and long distance call cost expenditures
Stable communications between company’s offices throughout different cities and counties
Personal SIP/IAX/POTS/SMS Gateway services for A-Z calls. Pre-paid credit. Direct SIP/IAX calls or calls via POTS gateway using analog/mobile lines + pin. Callshop solution and DIDS from all regions in Czech Republic available.