Is there a simple way to indicate that contacts are open?

Thread Starter


Joined Mar 26, 2014
Using a neon lamp and resistor across 120 volt contacts with a load resistor in series, the neon will light when the contacts open.
What is the maximum resistance of the load resistor?
Please provide help calculating.
Is there any other discrete device besides a resistor which could be used in series with the contacts and still light the neon when the contacts open?
No relays allowed!

No this is not homework.
It's just a problem I was thinking about going to work yesterday.