I have make a 5 input voting system with 8x1 multiplexer, but its is giving a grey dot on its output. Can anyone please explain why is it coming and how to remove it?
I have attached the screenshot of the circuit.
Please assist me with my semester project.

 

what simulator is that?

 

what simulator is that?

Proteus 8

 

Well, you've supplied very little information, but does the undefined load on the right reflect back as an undefined state on Z? Perhaps if you defined a load it might help.

 

Simply try to use a "normal" logic device for example 74xx151 instead of an ECL logic family.

 

Or a CMOS 4000 series device.