# How to create 1:4 Demux diagram using 1:2 Demux?

By 2m = n where m is the number of select lines and n equals the number of outputs (4) I found that I will need 2 select lines in total. But, I don't even know how to start drawing the actual circuit diagram using the base 1:2 demux, something that looks like this:

I'm not entirely sure on how I would chain 2 1:2 demuxes to create that 1:4 demux functionality.

EDIT: This is what I think it should look like

• Sounds like a homework question. Consider starting with two 1:2 muxes to provide output for 4 channels all running from one input m. Now figure out a digital logic circuit that would control the select lines to provide the right output on the 4 channels. – EasyOhm Jan 28 '19 at 23:09
• Just gave it some through. May need to use three 1:2 muxes if powering them off is not an option. – EasyOhm Jan 28 '19 at 23:16
• @Gonzik007 I created a diagram using AND and NOT gates, but I need to make one using the demux symbols. Check my edited post too see what I think it should be like – PeraltaLearns Jan 28 '19 at 23:19
• Your new picture shows the demuxes pointing the wrong way, with the wrong number of inputs, compared to your first symbol. So there is no way to tell what you have. – WhatRoughBeast Jan 28 '19 at 23:40
• @WhatRoughBeast Ok do I just have to flip the trapezoid to face the other way? And why is it the wrong number of inputs when I know I have to selector lines and input is always one? – PeraltaLearns Jan 28 '19 at 23:59