Choosing a hosted PBX service provides advantages in several areas where traditional PBX phone systems are weakest. Hosted PBX delivers PBX functionality as a service, available over telephone and/or the internet. The first hosted PBX was introduced in late 1997. Users contract for PBX services from a hosted PBX provider. Today, it is possible to get hosted PBX service with more features than were available from the first systems of this class, or to contract with companies that provide less functionality for more simple needs.

Now using a Hosted PBX Phone System you can have all of the features of the best telephone and voicemail systems, with no equipment to buy, maintain or outgrow. The hardest mainstream features to get in a hosted system are real Automatic Call Distribution (ACD) instead of simple hunt groups, flexible company directories, call transfers between extensions (or to an operator or an ACD queue), and real-time system monitoring. There are many other advanced functions that only a few providers have been able to make available. Web-based administration tools are the norm for hosted PBX services. Adding new users, changing extensions, and changing hunt groups or call queues is as easy as a point and click.

A Hosted PBX phone system can be configured to utilize your current voicemail, for example, transferring calls to your cell phone and letting the call roll into your cell phone voicemail if not answered. A hosted PBX usually can handle a higher number of calls. If the caller enters an extension they will be prompted to stay on the line while their call is transferred. If you answer you will have the opportunity to accept/reject the call. After accepting a call you can transfer the caller back to voice mail or to another extension. If the lines are busy or not answered the caller will hear the voice mail greeting for that extension and be able to leave a message. In addition, hardware PBX buyers are on usually a tight budget and buy small systems that can’t grow. But there is no capital outlay for hosted PBX services, and extensions can be changed as needs change. Hosted PBX customers pay only for what they need.

There are other advantages that a hosted system has. The most important is the ability to route calls to any phone, rather than just phones wired to the PBX inside the office. Other major advantages of hosted PBX include lower entry cost, support costs, greater ease of management, flexibility, and improved scalability. No longer will your traveling employees feel out of touch. The right hosted PBX service can make their cell phone into a seamless part of the company telecommunications infrastructure: calls to their extension will ring through to their cell, and they’ll be able to transfer and forward calls as usual.

The integrated voice features, for example unified messaging and “click-to-dial”, became available with circuit-switched PBX systems. Complex coordination of voice and data networking environments are required. IP network level however, eliminates much of this complexity, attaining results which are lower costs from consolidating equipment and rapid integration with business applications. The requirements necessary for IP PBX systems to successfully integrate with a packet network are:

•Reliability to minimize the loss of voice packets and control network delay.

•Quality of Service (QoS) to ensure that voice packets are transmitted through each network element with the correct priority relative to other types of packets.

Real Time Protocol (RTP)

RTP uses a set of Internet Engineering Task Force (IETF) standard protocols for reliably transporting voice, video, and data among participating parties across a packet network. Comments requests include:

•The RTP protocol (RFC 2550), carrying voice that has been encoded using ITU G.711 or an alternative codec system. The protocol includes time stamps and sequence numbers, “jitter management”.

•RTP for dual tone multi-frequency digits carries encoded tones used in interactive voice response (IVR) applications.

•RTP for redundant audio data specifies a mode of transporting same sequenced audio patterns to effectively reduce the number of packets transmitted.

H.323

H.323 – a set of related ITU recommendations that describe the architecture for multimedia communication over a packet-switched network. Key factors:

•H. 323, defining the multimedia infrastructure, including the role of devices, gateways and gate keepers.

•H. 245, specifying the call control processes for establishing and terminating a multimedia session, which includes the exchange of the capabilities supported by client devices.

•H. 450, specifying a set of supplementary devices, like call transfer, hold, message waiting etc. This protocol is useful communication between clients without the aid of a switch.

Session Initiation Protocol (SIP)

SIP is an IETF standard protocol helpful for initiating an interactive user session that carries multimedia subjects. The SIP architecture comes with a method for delivering connections for users at any location where he/she is registered. In contrast to the H.323, SIP uses an extensible text-based format, similar to HTTP. SIP, being the basis for multi applicable programs including instant messaging and gaming. It can function as a standalone call control protocol or together with H. 323.