on-off rule
nounUK /ˌɒn ˈɒf ruːl/
US /ˌɑːn ˈɔːf ruːl/
A rule that says something can only be fully on or fully off, with nothing in between.
The light switch follows an on-off rule, so it is either bright or dark.
OTHER MEANINGS
2. A control strategy where a device switches fully on or fully off to keep something near a target.
The heater uses an on-off rule to keep the room warm.
3. A simple decision rule that treats a situation as either acceptable or not acceptable.
The club's on-off rule means you are either a member or not.
4. A behavior pattern of switching abruptly between two extremes.
His on-off rule at work made him either very busy or completely idle.