If it is a high limit such as a temperature alarm then the current temperature is below the limit.
Normally open contact numbers.
If it is a switch then it is off.
When voltage is applied this contact opens and interrupts current.
Din 72552 defines contact numbers in relays for automotive use.
When the energizing force is present the contact will close.
87b normally open contact.
If it is a relay then it is not energized.
An alternate notation for form a is spst no.
Form a contacts make contacts are normally open contacts.
Normally open no contacts allow current when the relay or contactor is energized.
Energizing it and switching it on will close the contact causing it to allow current flow.
Normally open is a contact that does not flow current in its normal state.
The contacts are open when the energizing force magnet or relay solenoid is not present.
Of these contact forms the following are particularly common.
In other words when voltage is applied to the relay contactor terminals this contact closes.
85 relay coil 86 relay coil 87 common contact.
Normally closed nc contacts allow current through when the relay or contactor is not energized.
A relay contact in the ladder diagram can be normally open or normally closed and there is no limit to the number of contacts a relay can have.