Enhanced Presence Sensors and Receivers
In the unified communications system, presence data for a user can be collected and published from a variety of input sources. Each of these possible sources is described in more detail in the following sections:
Private Branch Exchange (PBX)
A PBX is a telephone exchange that serves a business or office, as opposed to a telephone exchange that a telephone company operates for many businesses or for general consumers. Most legacy public switch telephone network (PSTN) desktop phones are connected to a PBX system.
Remote Call Control (RCC) Gateway
When users take phone calls on legacy phones, the RCC gateway acquires the off hook/on hook state of the user's desktop phone and publishes it to Office Communicator.
Microsoft Exchange Server
Microsoft Exchange Server is a messaging and collaborative server product. Exchange Server provides calendar information, such as a user's working hours, out of office information, free and busy data, and meeting details to enrich the user state. Office Communicator acquires this data from MAPI or from the Exchange Web Services interface and publishes the data to Office Communications Server.
Microsoft Office Communicator
The Microsoft Office Communicator 2007 R2 client software integrates voice, IM, video, live data communications, and presence awareness with other Microsoft Office applications. Microsoft Office Communicator publishes the user state, phone state, calendar state, and device state. The phone state is acquired through the RCC interface for phones connected to a PBX or from Communicator when a user places or receives a VoIP call. Communicator also publishes the device state when a user's computer goes from active to inactive to idle. In addition to publishing presence information, Office Communicator 20007 consumes presence information from Office Communications Server by subscribing to the user state of other contacts. Office Communicator is the only client that publishes the calendar state of a user. Note that Communicator Mobile and Communicator Web Access consume the calendar state data and show activity such as In a Meeting, but Communicator is the only client that pulls data from Microsoft Exchange and publishes it to Office Communications Server.
Office Communications Server
Microsoft Office Communications Server 2007 R2 is an enterprise-grade server that provides the backbone for all real-time communications within Microsoft Office. Office Communications Server sits at the heart of the unified communications platform. All the endpoints register, publish their user state, and subscribe to other contact's presence information on Office Communications Server. When users subscribe to a presence contact's user state by adding the contact to their Communicator Contact List or opening the contact's Contact Card, Office Communications Server provides presence information that is filtered based on the permissions assigned to the user.
Office Communicator Mobile
Microsoft Office Communicator Mobile is designed to extend the reach of Office Communications Server 2007 R2 to Windows Mobile software powered devices. Office Communicator Mobile publishes user state, device state, and phone state, if data connectivity is available. As with Office Communicator, Communicator Mobile also subscribes to the user state of other users.
A variety of IP phones are available for the unified communications system. An IP phone is connected to the LAN through an Ethernet port. An IP phone is a VoIP endpoint, so it can subscribe to others' presence information and can publish user, device, and phone states.
Communicator Web Access
Communicator Web Access provides browser-based access to Office Communications Server. It is useful when users do not have access to Office Communicator. Communicator Web Access can be enabled for access over the Internet or from within an organization's firewall only.
Microsoft Office Applications
Some applications in the 2007 Microsoft Office system release, including Microsoft Office SharePoint services and Microsoft Office Outlook, use enhanced presence information to enrich the user collaboration experience. Because these applications use the Office Communicator API to retrieve enhanced presence information, Office Communicator must be installed on the computer where the applications are running.
Third-Party Unified Communications Clients
Third-party unified communications clients or middle-wares can also function as the sources or receivers of a user's presence data. Such applications include those built on top of Unified Communications Client API, Office Communicator Automation API, and Unified Communications Managed API. These applications can publish the user's presence information at the user's request or when user activity or machine state changes. They can also subscribe to receive the published presence information provided that the subscriber is granted such permissions.