How to Incorporate a Switch Activated by Zero Voltage in a Circuit?

[Ry122]

I have a circuit in which I have a constant voltage passing through until I hold down on a button at which point the voltage drops to zero. When I let go of the button the voltage returns to normal. I need to add to the circuit a switch which activates when a voltage of zero is passing through and remains turned on until a voltage of zero is again passing through.
How Can I do this?

 

[Integral]

Google Normally Closed Switch.

Multi pole relays have both normally open and normally closed contacts. Look for NO and NC on the case switch diagram.

 

[N.Saravanan]

I have a circuit in which I have a constant voltage passing through until I hold down on a button at which point the voltage drops to zero. When I let go of the button the voltage returns to normal. I need to add to the circuit a switch which activates when a voltage of zero is passing through and remains turned on until a voltage of zero is again passing through.
How Can I do this?

Voltage cannot pass through components in a circuit. Voltage is a quantity measured across terminals in a circuit. Only current can pass through components in a circuit. Any way from your question I guess you may have to use a negative edge triggered Toggle Flip Flop. The output of toggle flipflop should be connected to a relay.