A. To make sure the IT-TEL Box work effectively, powered by DC 6V, no additional power needed. B. Support almost all the analog PSTN telephone with AC power. C. Support almost all the cordless PSTN telephone with AC power (Wireless DECT telephone most recommended, faster and better voice quality ) D. Support all the standard sound card jack with microphone audio-in and speaker audio-out ports and the sound card has been installed properly on the personal computers. Audio device driver installation is completed under IBM compliant Windows PC, Mac or Linux platforms. E. Support all the Internet voice chat programs under all operating system: Windows 98/ME/2000/XP, Mac, PowerBook, iBook. F. Extended microphone-in and speaker-out jacks to connect another headset or external speaker for better hand free talking condition. G. Easy plug-and-play hardware installation