An Inverted Contact represents a normally closed contact condition. An Inverted Contact can be:
An Inverted Contact condition can be from an external input device (for example: a push button) or from an internal input system element (for example: SB 50 Key +/- is pressed).
An emergency light contains an example of an Inverted Contact.
Normally there is power flow through the emergency light's Inverted Coil and the light stays off.
During an electric power outage, the power flow through the Inverted Coil stops and the emergency light comes on.
During the system scan, the processor evaluates the program elements net by net.
If the Inverted Contact address (power supply) is ON (logic 1): power will flow through the Inverted Contact. The emergency light will stay off.
If the Inverted Contact address (power supply) is OFF (logic 0): power will not flow through the Inverted Contact. The emergency light comes on.
If the power outage ends and power flow is returned to the Inverted Contact, it will close again and the emergency light will go off again.