How does the switching decoder work

Thread Starter


Joined Nov 28, 2006
How does the switching decoder work?

I mean in digital operation (0=off,1=on).Using transistor as a switch.

btw,Im a very new babe.


Joined Nov 17, 2003
A quick search of the net indicates that a "switching decoder" is a normal decoder featuring one or more relays. Other than that I cannot find any proper information regarding how one would work.



Joined Apr 20, 2004

If you're just concerned with the single transistor, remember that a logic 0 is also 0 volts, while a logic 1 is a positive voltage - usually 3 to 5 volts, depending on the logic family used.

In the case of a transistor, it is going to be in a common emitter arrangement, so the voltage on the collector will be 0 when the transistor is on - a logic 0. When the transistor is off, the collector will have the full voltage on it, for a logic 1. It just switches between those two states.


Joined Jan 28, 2005
Greetings eggtree,

I too am unfamiliar with the term "switching decoder". Perhaps it is just a matter of terminology.

If you are referring to a specific device then it would be helpful if you can provide a part number and manufacturer for the device so that we will have a place from which to begin assisting you with your inquiry.

If you are referring to a process or technique then it would be helpful if you could elaborate.


Thread Starter


Joined Nov 28, 2006
Sorry for the confusion as a new babe iand m not good in expressing technical things.

Currently, im in the planning stage of a project.There are 4 on/off switch and 4 boards.Each time, only 1 board can turn on and the rest are off.

I will do up a truth table and use some transitor switch for the logic '1' ON and OFF '0'.

The problem is I do not know how the transitor is wire together.I m not asking for expert here to do my work. I just want to know the logic.

Example, some IC logic chips has got nothing but many wire up transistors. I just want to know how this work.



Joined Feb 24, 2006
Well one thing that comes to mind is four 4-input AND gates, one for each board. The board will be turned on IF the corresponding switch is closed AND the other three switches are open. Same logic for each board. I suppose you could do it with discrete transistors the way Diode Transistor Logic was done 45 years ago or so.


Joined Apr 28, 2004
eggtree, are you aware of how logic gates work? If so, then you simply need to view the data sheet for your ICs, which will show you what functions they perform and how to connect them.

Which brings up a question I thought of a while back...*goes to make new post*