Limited, or Out of Inputs?All TVs have a limited number of inputs, but some are much more limiting than others, especially if your set only allows for one external device. Whatever the situation, limitations surface in every home theater setup. Maybe your TV has three composite inputs but only 1 S-Video input, and you have 4 S-Video devices you wish to use. There is no way you can connect 4 S-Video devices to a TV with only one S-Video input directly, but there are devices you can use to make a connection like this possible.
If you have an older TV with a very limited amount of inputs, or have so many things hooked up that you've used them all, you can still add more devices to your TV in a variety of ways. Before you can begin, you'll need to determine what types of video connections you need to add. The most common video connections are composite (yellow RCA jack), S-Video (the one with the pins), and component video (the red, green, and blue RCA jacks).
Adding extra inputs is accomplished by the use of "audio/video switching". Rather than physically switching components manually, like unplugging your DVD player to plug in your VCR, you can add a device that offers many inputs and one output. This concept isn't much different from how televisions with multiple inputs work except it brings the concept to an external device. This way, all of your devices are connected, so there is no need to physically move cables from one device to another. All you need to do is select which of the connected devices you wish to view.
Common MethodsSwitching Through a Receiver
The cheapest way to do this is to take advantage of any components you may already own that have audio/video switching capabilities. The most common device you may own is a home theater receiver. In many cases, receivers allow you to plug multiple audio and video signals into them, and provide a single video output to your TV, assuming you use the same video connection for each device. Some advanced receivers even allow you to mix incoming signals and still provide a single video output. When done this way, the device selected on the receiver is the device that will be output to the display.
Most of them switch composite, many will do S-video, and some component. So, if you are out of S-video inputs on your TV, you may be able to plug all of your S-video devices into your receiver and plug one S-video cable from your receiver into your TV. If your receiver doesn't offer this capability, then you might want to consider an upgrade.
Using Your VCR
If you are short a composite input, and don't have an A/V receiver, you can often get by if you plug the device into an open input on your VCR. Most VCRs have at least one composite input on either the front or back of the unit. (NOTE: You cannot pass a DVD player's signal through a VCR due to the MacroVision copy-guard system.) This can be a pain to setup since it involves setting the input on two devices, but it can get you by in a pinch.
External Switch Box
If you have no devices that are capable of switching the connection you need, you could purchase an external A/V switch box. There are many for composite and S-Video signals, but ones that switch component are still somewhat limited. Nonetheless, they are out there, and can affordably add a multitude of inputs (usually four) for more devices. These work by allowing you to plug many of your devices into a single box, and making one connection to your TV and/or receiver. To view the signal from a device, you usually press a button on the front of the box. They're really easy to use, but often make you get up and press buttons to switch devices. There are remote capable ones, but are usually more expensive.