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White Paper

Selecting the Right SIP Phone for Your IP PBX

By Gary Audin

May 5, 2014

There are many Session Initiation Protocol (SIP) phones on the market manufactured by IP PBX vendors and third

parties. Selecting the best phone for your use is both a technical and a business decision. The selection process

starts with the choice of SIP phones based on technical requirements. Once the SIP phones have been selected,

possibly from more than one manufacturer, then the manufacturer’s geographic coverage, sales channels and

financial strength will narrow down the potential choices. This paper will guide you through this process by first

providing an understanding of the SIP phone landscape and then the process for phone selection.

SIP for VoIP

SIP is a standard signaling protocol that is commonly implemented for Voice over IP (VoIP) communications. Many

proprietary access and signaling protocols have been developed for VoIP. The development of SIP has brought a

level of standardization to IP phones and led to the creation of the SIP phone. SIP can also support unified

communications (UC), multi-media, video, chat, conferencing and instant messaging (IM). As a result, SIP phones

are largely displacing legacy analog and digital phones.

SIP Phones and the IP PBX

SIP phones are designed to communicate directly over an Ethernet LAN network or through a Wide Area Network

(WAN) IP network connection that is either private or public like the Internet. A SIP phone is fully interoperable with

the Internet Protocol (IP).

An IP PBX is the controller of the phone calls. It is the modern replacement for the legacy PBX and telephone key

systems. An IP PBX is a server with call manager software. The server can be located at a data center or even in

an office closet.

The call manager software can be proprietary or it can be software-based like Asterisk

by Digium

. Asterisk is a

free and open source framework for building communications applications. Asterisk software turns a computer into

a communications server and powers IP PBX systems, VoIP gateways and conference servers.

The IP PBX communicates over IP and Ethernet networks. Locally connected SIP phones connect through a LAN

switch to the server. Remotely located SIP phones connect through a LAN, connected to a router that is connected

to an IP WAN. The call manager sets up the voice call and manages its operation, but the voice does not go

through the call manager. The call manager sets up a peer-to-peer, SIP phone to SIP phone connection over the

LAN if the call is local or over the WAN to a remote location. The call manager is in an idle state during the call and

disconnects the voice connection when the call completes.

If a call needs to be transferred to the Public Switched Telephone Network (PSTN), then the call must be routed

through a gateway that converts the voice and signaling to a PSTN compatible format. The SIP signaling and VoIP

are converted in the gateway and the call goes out over the PSTN.

SIP Phones and the Cloud Communications Services

There are literally hundreds of cloud/hosted communications service providers in the world. Most of these have selected

SIP phones as their endpoint devices. Although there have been some proprietary IP phones selected, the providers

are moving to standardize on the SIP phone. Therefore, selecting a SIP offers a wide range of service providers to

choose from that can support SIP phones.

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VTech is the global leader in electronic learning products from infancy to preschool and the world’s largest manufacturer of cordless phones. It

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VTech IP Phone User Manual

Browse online or download User Manual for IP phones VTech IP Phone. Selecting the Right SIP Phone for Your IP PBX

Summary of Contents

More documents for IP phones VTech IP Phone

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