ZyXEL Communications IP PBX X6004 - Manual (Page 42)

Chapter 1 Introduction
X6004 User’s Guide
42
Figure 1 IP PBX Example
The X6004 can function as a stand alone telephone switchboard for a small
organization. It can also supplement a legacy PBX within an organization by
providing VoIP telephony features.
1.1.1 Voice over Internet Protocol (VoIP) Implementation
The X6004 uses SIP (Session Initiation Protocol) to communicate with other SIP
devices. SIP is an internationally-recognized standard for implementing Voice over
Internet Protocol (VoIP).
The following figure shows SIP devices communicating with the X6004.
A: IP Phones - Telephones that convert voice into IP packets and vice versa (for
example ZyXEL’s V-500).
B: Softphones - Software-based phones installed on PCs.
C: VoIP Gateways - Devices (for example ZyXEL’s P-2302HWUDL) with built in
SIP processing which allow traditional analog phones or cordless phones to use
them as a link to the IP PBX.
D: ATAs - Analog Telephone Adapters (for example ZyXEL’s P-2024) aggregate a
large number of analog phones and convert their signal into IP packets.
E: Peer IP PBXs - Other SIP based IP PBXs with which you communicate over an
IP network. This allows you to call the telephones connected to the peer IP PBX
without going through a telephone service provider.
PSTN
Internet
ITSP
PSTN/ISDN