AV Technology - October 2008 - (Page 36)

UNDERSTANDING IoIP to Ethernet and IP traffic sent to all devices using an address set to all binary ones.) Windows devices like to browse the network using such broadcast packets. Many management and control software systems use broadcasting as a simple means to send information to all of the devices associated with their applications. Even network management software often uses such discovery techniques. While broadcasts are used as a standard method of communicating in data networks, they can cause a disruption to IP-based audio that is expected to be delivered and processed in an even and efficient manner. Some of the systems mentioned here support IP quality of service (QoS) methods. When this is used, the source station marks the packets with a code that is stored in the IP header. Each router in the network recognizes that mark and expedites the packet in deference to other packets that aren’t marked. While QoS techniques are widely deployed, not all routers will be configured to read and process these marks. You’ll need to work with the IT router technicians to make sure this happens. The most significant feature to check out is how the devices are powered. If they include power over Ethernet support (PoE), the IoIP devices will get their power from the switch to which they are attached. If not, you’ll need to pay a contractor to make sure there is a power receptacle near by, even if it’s in the ceiling. The switches you purchase will need to support PoE also. WHERE IS IP INTERCOM HEADED? Customers will surely begin to ask for certain features that are standard in other IP devices. WiFi compatibility will be high on the list. Using wireless, the teacher could answer an intercom call from a handheld device. The doctor could ask the nursing station to page another doctor without finding a wall-mounted unit. IP multicasting will be a necessity on all of the systems. Currently, a few manufacturers such as Barix and Digital Acoustics support it, but others do not. When a broadcast is done without multicast capability, the amount of bandwidth needed is the amount needed by a single call multiplied by the number of stations the broadcast needs to reach. In other words, if one call takes 80 kb/sec, broadcasting to 20 stations takes 1.6 Mb/sec. That’s too much. With multicasting, the bandwidth will be reduced to 80 kb/sec on each link in the path between the source and the output stations. Another future enhancement is likely to be video. There are some situations in which adding videoconferencing would be just a convenient extra, but security concerns may make it a necessity for schools, hospital lobbies, and companies to screen all entrants. Nearly every manufacturer we talked to has this on the list of future enhancements. Of course, if intercom moves to the desktop, calls and pages can be answered from there without moving even standing up. Since the PC is connected to the IP network, it’s entirely feasible to do this. Phil Hippensteel is an industry consultant and assistant professor at Penn State University. He can be reached at pjhippen@comcast.net. 36 | AV TECHNOLOGY http://www.spcontrols.com http://www.spcontrols.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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