AV Technology - October 2008 - (Page 33)

A VOICE CALL IN MOST IoIP SYSTEMS CURRENTLY USES ABOUT 80 KB/SEC OF BANDWIDTH PER DIRECTION PER VOICE. THIS ISN’T MUCH BANDWIDTH ON A LAN, BUT COULD BECOME A SIGNIFICANT ISSUE ON WIDE AREA NETWORK CIRCUITS. often the G.711 codec commonly used in VoIP systems. These packets are sent from one end to the other, often at the rate of 50 packets per second. When the voice conversation changes directions, the packets are sent in the opposite direction. A voice call in most IoIP systems currently uses about 80 kb/sec of bandwidth per direction per voice. This isn’t much bandwidth on a LAN, but could become a significant issue on wide area network circuits. The network used to support intercom can be the existing data LAN, assuming sufficient bandwidth is available and its characteristics are conducive to carrying voice and other real-time data, or you can build a separate network with inexpensive Ethernet switches. The most expensive part of a separate network is likely to be the dedicated cable runs, but, like conventional data networks, your intercom network could now use fiber in its backbone and cover very long distances between buildings. After the intercom signal is in IP packets, it can be carried over the internet. However, each of these new extensions of the intercom network brings with it significant concerns about performance and security. WHO BUILDS IP INTERCOM? Extron offers two approaches to IP intercom that fall within its MediaLink family. The 100 Series endpoints require an MLC 226 IP MediaLink controller. These would be used when the room needs AV control for a projector and a recording and play-out device. The 200 Series devices operate in standalone mode. On a one-button model, you can only push to talk. On a four-button model you can push to talk to four locations. Extron Electronics also supplies a software control package called the IP Intercom Help Desk. You can use it and a PC with a headset to communicate to any room equipped with IP intercom. The Help Desk software allows you to configure the entire system from a single location. There is an auto-discovery feature that allows the easy addition of new stations. You can also create announcements as MP3 files and distribute them to individual rooms or groups of rooms. Swiss manufacturer Barix AG builds a family of products to deliver audio over IP networks. It does IP intercom as a subset of that functionality. The key device is the Annuncicom 100. It acts as an interface between input devices such as buttons, microphones, and audio sources and out- october 2008 | AV TECHNOLOGY | 33 http://www.iavi.com http://www.iavi.com

Table of Contents Feed for the Digital Edition of AV Technology - October 2008

AV Technology - October 2008 Contents Precedent Corporate: Residential AV Does Not Equal Commercial AV Government: Funding Problems? Education: DIY ISP.EDU, Part Two The Cost of Bandwidth Star Grounding Wars Understanding IoIP How to Equip a Smart Classroom Two Rooms With A View From Primitive to Professional Product Review:�Visionary Solutions AVN 420 Encoder Product Spotlight: Document Cameras New Products Ad Index AV MO: Using Infrared Microphones

AV Technology - October 2008

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