To follow the other contributors to this topic, the following information are put out here for giving advice.They might sound useful for you. To create a reliable predictive dialer system, you might be interested in related sample programs and source codes. I would recommend to check it out here: voip-sip-sdk.com/p_439-call-center-predictive-dialer-voip.html It is based on an sdk providing flexibility with lots of systems and compatibility with many pbxes that many other sdks lack. I have tried it out and it is still working without problems.