Here I give you clear idea about a multiplexer and the working principle of it. To know about multiplexer we have to know about what is a multiplexer and how it work?
A multiplexer commonly called MUX is also called a data line selector. And MUX is a combinational circuit with more than one input line, one output line and more than one selection line. Now late take a practical example to understand the working function of MUX. Let we have three different supply lines one has 50V DC another two has 100V and 150V respectively. And we have mechanical rotary switch shown below.
Now see if we select 50 Volt line by mechanical rotary switch then output line gets 50 Volt. In this way we can get different output voltage by rotating mechanical switch.
By above mention process multiplexer selects binary information present on any one of the input lines. And as like mechanical rotary switch for selecting input we use select line and different logic state at the selection line, and routes it to the output line. If there are n selection lines, then the number of maximum possible input lines is 2n and the mux is referred to as a 2n-to-1 or 2n ×1 MUX.