Inputs and Outputs
Inputs and outputs
Last modified: January 10, 2005Data interfaces
RGB/VGA
Found on: Nearly all projectors and computers.
The 15-pin VGA interface is what most people use to connect a laptop to a projector, and rightly so. Its design gives the RGB signal's red, green and blue color channels dedicated pins, as well as pins for sync information within the interface itself. And you can use this connection for both computer graphics (think Microsoft PowerPoint slides) and video (either embedded in PowerPoint or through a component-to-RGB cable connection.
DVI
Found on: Smaller projectors and some notebook computers.
Also known as: Digital Video Interface.
The 18-pin DVI connection began appearing on projectors a few years ago, and has recently found its way to laptops. Though still popular, the VGA connection uses an analog signal. DVI can provide a digital-to-digital uncompressed signal (DVI-D), so a projector can immediately sense the signal's resolution and clock speed and, in theory, provide a more electronically precise picture.
According to Ken Burgoyne, an engineer for the St. Paul, Minn.-based systems-integration firm SPL, DVI isn't used often in the installation world because it's an expensive choice. "This connection uses silver instead of copper inside the cables, and 75 feet of DVI cable costs about $1,000." Also, a DVI signal can't travel as far as an RGB signal, so although DVI may be fine for tabletop connections, it's not always the best choice for installation environments.
USB
Found on: Projectors, laptops, digital cameras, some camcorders and many computer peripherals.
Also known as: Universal Serial Bus.
When it arrived in the mid-1990s, marketers made the USB standard sound like the end-all and be-all of computer interfaces, ushering in a new era of plug-and-play simplicity. For the most part, USB has delivered on its promise, but nearly every computer user can recall a USB driver conflict nightmare, in which plug-and-play quickly turned to "plug-and-pray." In addition, USB's 40 Mbps transfer speed was quickly surpassed by its speedier nemesis FireWire, which transfers data roughly 10 times faster.
The recent rollout of a swifter version of USB, known as USB 2.0 – assisted by improvements in Microsoft Windows XP and Mac OS X operating systems – has made the USB interface competitive again. USB 2.0 provides a transmission speed of 480 Mbps, enough to surpass FireWire. Plus, the connections are more stable now, so your mouse, scanner, printer and other peripherals can be plugged in and out with nary a hitch.
FireWire
Found on: Projectors, computers, camcorders and external hard drives.
Also known as: IEEE-1394, i.Link.
The technical term for this interface is IEEE-1394, and Sony calls it i.Link. But most of us know it by its birth name given by Apple Computer – FireWire. Its plug-and-play reliability and 400 Mbps data-transfer speeds have made it the darling interface of video enthusiasts and external hard-drive manufacturers.
To compete with USB 2.0, however, Apple is now rolling out what it calls FireWire 800, which has an 800 Mbps transfer rate. Adoption of FireWire 800 will likely be more of a challenge, though, because the interface is different from FireWire 400 (what Apple has now dubbed the original FireWire). There are a number of adapter cables available, but you can't get the speed of FireWire 800 unless you have a native FireWire 800 port on both ends of your connection. FireWire 800 ports are now appearing on new Macintosh computers and some external hard drives, but so far, that's about it.
Ethernet
Found on: Computers, larger printers, and an increasing number of projectors.
Also known as: 10Base-T Ethernet, 100Base-T Ethernet (Fast Ethernet).
At first glance, the Ethernet's RJ-45 port appears to be a glorified phone jack. It's larger than a modem port's RJ-11 jack and can connect a device to a local area network (LAN). IT departments love it because Ethernet puts their installed Category-5 cable to use, allowing them to inexpensively network several computers and peripherals for maintenance and sharing of resources and files.
Ethernet connections are appearing on projectors as well, enabling them to hook up to a network like any other peripheral. According to Ken Burgoyne at SPL, "We're starting to see a lot of projectors on networks. CAT-5 cable can now handle video and high-resolution signals, and it's found in every building. I see this being the wave of the future."
Burgoyne admits that adding a projector to a LAN is still a head-scratcher for some IT professionals. "If we tell them we're putting a projector on their network, they ask why. They just don't see the benefits yet." Burgoyne expects that in a couple of years most projectors in a company will be happily co-existing on the company LAN, just like the printer fleet.
Serial ports
Found on: Computers, projectors and printers.
Also known as: RS-232, mouse, PS/2.
Serial ports come in several shapes and pin configurations. There's the serial/RS-232 port, a 15-pin interface much like the VGA interface. There's also a PS/2 or mouse connection that's rounded like an S-video connection but used for hooking up a mouse and keyboard. Serial ports are dedicated connections that are slower in transmission speed but offer control of the device through traditional peripherals, such as a mouse or keyboard. While some computer manufacturers have moved mice and keyboards over to USB ports, many still go with serial because it's reliable and allows the user's USB ports to remain free for other devices. Also, RS-232 connections are used in some projector installations to hook the unit to a room-control system.Video and audio
Composite video
Found on: Projectors, some notebook computers and many pieces of AV equipment.
A yellow-colored RCA port refers to composite video, a nearly universal video connection in the AV industry. Developed with the advent of color television sets, the job of a composite signal is to combine the luminance, a video image's black-and-white information, with the chrominance, its color information. All fused together, the composite connection is a quick and easy way to get all the picture information from its source into a projector or monitor.
Using a composite-video connection for high-resolution and larger displays is not always the best choice, however. With composite, the receiving device must separate the chrominance and luminance information and reassemble it to form a picture. This process can introduce signal noise, affecting image quality. Still, composite-video cable is inexpensive and accessible and will provide reasonable picture quality in most cases.
S-video
Found on: Projectors, laptop computers, DVD players, and Hi8 and S-VHS VCRs and camcorders.
Also known as: Y-C or Y/C video.
The S-video connection was developed in the 1980s to address shortcomings of composite video. S-video keeps the luminance (black-and-white information, also known as Y) and chrominance (color information, also known as C) separate, decreasing the opportunity for the introduction of signal noise. S-video provides a higher-quality connection than composite-video does, and most projectors are equipped with an S-video port so VCRs and DVD players can take advantage of the superior signal.
Component video
Found on: Some projectors, particularly installation models, DVD players and high-end video monitors.
Component video divides a video signal further, using three cables instead of one. One cable carries the luminance (black-and-white) information, one carries the blue-channel information and the other, the red-channel information. When combined with the luminance channel, the blue and red channels mathematically extrapolate the green channel to complete the picture.
The three parts of the component-video connection are often color-coded red, green and blue, and can be found on most DVD players, as well as on some VCRs and projectors. Component connections are considered better than both S-video and composite-video. Also, because all DVD video content is recorded in component video, a component connection displays a video DVD in its native format. Note: Some projectors provide a component-to-RGB connection cable to give presenters the advantage of component video without requiring all three ports on both ends.
RGBHV via BNC connectors
Found on: Large-venue projectors and high-end video displays.
Few interfaces look as intimidating as the five-cable RGBHV (for red, green, blue, horizontal and vertical), which uses a twist-locking BNC connector for a snug fit. Similar to the component-video connection, this interface separates the video signal into its color information, plus specifications for horizontal and vertical sync. As a result, the connection can handle any video signal, no matter what the resolution, and do it with little or no signal noise. Normally, only large-venue installation projectors that show a lot of video use this high-quality version of component video.
Audio connections
Found on: Projectors, computers and most AV equipment.
The audio connections on a projector, and to some extent on laptop computers, are little more than a backup when a quality connection isn't an option. In most cases, its an RCA connection with red and white jacks, indicating stereo left and right channels, or one audio jack, indicating a monaural connection. Occasionally, on lightweight projectors and some small digital camcorders, you will find an audio mini-jack like the ones used for small headphones.
In most cases it is assumed that if you're striving for the best possible video connection through S-video or component connections, you're not going to pair it with lousy sound. As a result, most boardrooms, conference rooms, training facilities and home-theater setups route the audio signal through separate devices, such as receivers and amplifiers, and then to high-quality speakers to ensure that the beautiful picture is accompanied by beautiful sound.
Adopted from Presentations magazine.