What Is Unified Communications?
Microsoft unified communications technologies tear down the walls that separate telecommunications and computing—and they do it with software that takes advantage of your existing telecommunications infrastructure.

Microsoft unified communications technologies are more than just VoIP. They break down all the traditional communications silos. Voice mail and faxes move over the network like e-mail. They arrive in your Microsoft Office Outlook inbox where you can sort, prioritize, and forward them, just like any piece of e-mail.
And when you're on the road, you can dial in over any telephone to hear your e-mail messages and your calendar. You can even access your Outlook address book and call anyone in it just by speaking his or her name.
Microsoft unified communications technologies use the power of software to deliver complete communications—messaging, voice, and video—across the applications and devices that people use every day.
Integrating the experiences you associate with the telephone—phone calls, voice mail, and conferencing—the work you do on a computer—documents, spreadsheets, instant messaging, e-mail, and calendars—has the power to fundamentally change the way people work.
Microsoft Office Communications Server 2007
Office Communications Server 2007 manages all real-time (synchronous) communications including: instant messaging, VoIP, audio and video conferencing. It works with existing tele-communications systems, so business can deploy advanced VoIP and conferencing without tearing out their legacy phone networks.
Microsoft Office Communications Server 2007 also powers presence, a key benefit of Microsoft unified communications that unites all the contact information stored in Active Directory with the ways people communicate.
With presence, you can see at-a-glance if someone is available and contact them with a click using instant messaging, a phone call or a video conference.
More informations about Microsoft Office Communications Server 2007.