ITSP Application With the Vigor2600V series router, people not only can make calls to/from other VoIP users across the Internet free of charge, but also can enjoy unlimited worldwide voice calls over Internet via ITSP (Internet Telephony Service Provider) gateway ( e.g. DrayTEL ). ITSP can transport telephone calls over the Internet, no matter whether traditional telephony devices, multimedia PCs or dedicated terminals take part in the calls, and no matter whether the calls are entirely or partially transmitted over the Internet. The useful application implements intercommunication among most popular ways of voice calls like VoIP, PSTN, GSM, etc.