Introduction:
In digital electronics, a multiplexer (MUX) is a combinational logic circuit that selects one of several input signals and forwards it to a single output line based on the value of selection lines. The number of selection lines determines the number of input signals that can be selected. However, in some cases, an enable or strobe input can be used to expand the number of inputs in a digital multiplexer.

Explanation:
A digital multiplexer is typically represented by the symbol "MUX" and has two main inputs: data inputs and selection lines. The data inputs are the signals that need to be selected, and the selection lines determine which input signal is selected. The number of selection lines in a multiplexer determines the number of input signals that can be selected.

For example, a 2-to-1 multiplexer has 2 data inputs (D0 and D1) and 1 selection line (S). The output of the multiplexer (Y) is determined by the value of the selection line. If S=0, the output Y is equal to D0. If S=1, the output Y is equal to D1.

Enable or Strobe Input:
An enable or strobe input is an additional input line that can be used to enable or disable the operation of a multiplexer. When the enable input is active (e.g., high or logic 1), the multiplexer functions as normal, and the selection lines determine which input signal is selected. However, when the enable input is inactive (e.g., low or logic 0), the multiplexer ignores the selection lines and outputs a default value (such as 0 or 1).

Expanding the Number of Inputs:
By using the enable or strobe input, it is possible to expand the number of inputs in a digital multiplexer. This can be achieved by cascading multiple multiplexer ICs together.

For example, let's consider a 4-to-1 multiplexer with an enable input. This multiplexer has 4 data inputs (D0, D1, D2, D3), 2 selection lines (S0, S1), and 1 enable input (E). The output (Y) is determined by the value of the selection lines when the enable input is active.

To expand the number of inputs, we can cascade multiple 4-to-1 multiplexers together. The enable input of each multiplexer is connected to a common enable signal, and the selection lines of each multiplexer are connected to different bits of a binary counter. This allows us to select one of the multiple multiplexers based on the value of the counter, effectively increasing the number of inputs.

For example, if we cascade two 4-to-1 multiplexers together, we can select one of 8 inputs (2 multiplexers * 4 inputs per multiplexer) using 3 selection lines (2 selection lines for the first multiplexer and 1 selection line for the second multiplexer).

Conclusion:
In conclusion, by using an enable or strobe input and cascading multiple multiplexer ICs together, it is possible to expand the number of inputs in a digital multiplexer. This allows us to select one of a large number of inputs based on the value of the selection lines and the enable signal.