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MillimeterWhat is a Networked Projector?
May 30, 2002 12:00 PM
From the outside, networked projectors don’t look much different from other models. The difference is in the projector’s operating system and menu structure. Through the use of serial (RS-232C) or TCP/IP protocols, a networked projector can be controlled from remote locations, provide instant status updates, and even download presentation software files for later viewing.
Sharp’s full line of installation LCD projectors support one or both of these protocols. The first (RS-232C) has been a staple of the systems integration industry for years, and is a low-speed (9600 baud) serial interface for direct control of projector functions. It can also be used to move large files and will even talk to other projectors in a multi-screen installation.
 Sharp's XG-P25/P20XU |
The second interface is better known in the information technology (IT) world. Transmission Control Protocol/Internet Protocol is the basis for Internet communications and the interface between devices in a local area network (LAN) or those in multiple networks. The limiting data rate of a TCP/IP interface is dependent on the network to which it connects, and those data rates can easily exceed 100 megabits per second (Mb/s).
To be considered “networked,” a projector must support at least an RS-232C interface. While not as fast as TCP/IP networks, the RS-232C handshake is sufficient to send and receive commands from projectors and obtain updates on the projector’s operating status. Multiple projectors can be daisy-chained and assigned unique RS-232C addresses so they respond only to those commands sent to them.
TCP/IP networking works much the same way, except at a higher speed. Each projector is assigned a unique IP address, just as a desktop computer, notebook, laser printer, digital camera, or server might be. As thousands of data packets flow through the network, each projector “grabs” only the packets addressed to it.
These packets might contain commands, status inquiries, or still images. By using standard interfaces such as Simple Mail Transfer Protocol (SMTP), each projector functions as both a server and a client, depending on which commands and functions are needed.
Wiring up either network isn’t a major headache. RS-232C control can use standard twisted-pair plenum wire, or Cat 5/6 multi-wire cable. IP-connected projectors use Cat 5/6 cable exclusively, and this type of cable is inexpensive and easy to install with crimp connectors. Best of all, it is the standard for other IP-connected devices within a network, so, tying into existing company or institutional LANs is a much easier job.
