What is described as an intermittent ignition?

The correct choice describes intermittent ignition as a system where the ignition source is activated only for a limited time during the startup phase of the burner operation. This means that the spark will turn off once it has successfully ignited the fuel, thus establishing the flame. This is an efficient method to save energy, as the spark isn't continuously active.

In comparison, other methods such as using a spark that remains on until the burner is completely shut off indicate a different ignition system—not intermittent, as that would mean the spark is active beyond the initial startup phase. Options describing automatic flame establishment and pilot light usage also don't align with the definition of intermittent ignition, as they suggest different ignition methods that do not rely solely on a startup spark.