Despite what it sounds like in common parlance, a multiplexor is not a machine that creates giant movie theater complexes. Rather, a multiplexor is a handy device that can bundle several data signals together for use in one giant transmission, using just one method of transmission. The result is a faster data stream, but one that needs some reverse engineering on the other side.
A multiplexor can come in handy when transmitting data in multiple signatures requires more money and/or time than a company or individual wants to spend. In these cases, a multiplexor does all it can to save time and money. However, the machine receiving the combined data stream must have a demultiplexor, which breaks the data stream back into its original parts for analysis.
To understand this process better, think of this sort of data transfer in real-world terms. Think of a series of pipes down which water flows. The water initially flows down several pipes but is funneled into just one pipe in the end. All of the water flows through that one pipe to the ultimate destination. At that ultimate destination, all of the water comes out through one pipe and is then distributed through multiple pipes.
Multiplexors involving from two to eight inputs are quite common. A multiplexor having more inputs in not unheard of. The same is true of demultiplexors.
A multiplexor is sometimes called a mux for short. In the same way, a demultiplexor is sometimes called a demux. Both are available for both analog and digital signal processing.
A multiplexor is commonly used in the transmission of communications signals. A video signal, for example, will have both a visual and an audio component. A multiplexor can weave both components together for the transmission process, and the demultiplexor on the other side can reverse the process. This kind of transmission is extremely common in both digital television and digital radio. In addition, analog transmissions such as FM radio use a multiplexor, adding subcarriers to the audio signal for modulation. This is known as MPX.