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An optical cable splitter is a device used to combine two or more optical audio signals into a single output cable. This allows multiple devices to work on a single audio system that only has one input socket. Although the user will not need to repeatedly unplug and replace cables, he will need to either press a switch to change the input source, or make sure only one source is active at a time.
Optical cable is one of two main types of cable used for digital audio signals, the other being known simply as digital cable. The optical cable transmits light signals rather than electrical pulses and can be distinguished by its transparent plug that will display a light when unplugged during use. Contrastingly, digital cable has a more traditional metal pin plug. Optical cable is also known as TOSLINK, which is the name of the transparent plug at the end. Sometimes optical cable is referred to as S/PDIF, though this should be avoided as the term covers the technology behind coding the audio signal and can equally apply to digital cable.
The need for an optical cable splitter most commonly arises among owners of a home cinema or surround sound system. Though most surround sound receiver/amplifier units will support optical cable inputs, many only have one such socket. In the past this wasn't a problem as consumers generally only had digital audio from a DVD player. Today many consumers also have digital audio capabilities on a cable or satellite television receiver or video games console. Without some form of splitter, the user would need to manually unplug and replug cables to change source, which can often be inconvenient if the sockets are not easily accessible.
An optical cable splitter simply takes the signals from two or more cables and can then output any of the signals through a single cable. In very simple terms, the device works by redirecting the light signal in a similar way to a periscope. Note that despite the name, technically an optical cable splitter is combining two or more signals rather than splitting one.
There are two main ways of handling the relay of the multiple input signals. One is through a physical switch that means only one input is "pointed" towards the output. The other is with switchless splitters, which pass through all the signals and thus will only work when only one input device is active. If two or more input devices are active the splitter will pass on all the signals, creating a useless output. Unlike with an HDMI high-definition video system, for example, optical signals don't carry a signalling pulse that can indicate which signal should be treated as active and take priority in a switcher.
There are two main potential problems to watch out for with an optical cable splitter that relate to the optical technology. The first is that the maximum distance of cable that will work reliably may be reduced, though this is unlikely to be a problem in a domestic setting. The second is that the need to avoid sharp bends in the optical cable may be a problem if you do not have adequate space for the splitter.