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Hi . I am a new kid on the block. I would like to build a studio warning light. When on air red led lights up and when off air green lights up. Can anyone help me with a simple circuit. Thanks Prof

You haven't said anything about how big or bright you want it to be and whether it is supposed to show the words "On Air" and Off Air".

The basic circuit would be like this:

You could replace the LEDs and series resistors with dedicated LED bulb replacement units which already contain the current limiting resistors or just with incandescent bulbs.

Thanks for the feedback. I do apologize for not being more specific.The idea is not to show on air and off air but just red and green. It will work with the output voltage of the sound desk In my case 12v. When the fader open it sends out 12v that can activate the circuit and i suppose the red led,but how do i activate the green with just one input voltage to the circuit?

That's a bit more complex.

When asking for help you need to give as much, good quality, clear and concise information up front as possible.

What does your 12V feed do when the fader is not open?

Go to 0V? Go high resistance (is it basically an on/off switch connected to 12V)?

How much current can your 12V feed source (supply) when at 12V and sink (have driven into it) when it is not?

You need to give people a specification to work to.

Better still a copy of the section of the spec or datasheet for your sound desk that describes this function.

Got a circuit diagram for this part of the desk, even a simplified one?

Can you draw it in CL?

:)