Meaning of symbols used in ABB contactor circuit
After searching around (https://search.abb.com/library/Download.aspx?DocumentID=2CDC131025D0201&amp;LanguageCode=en&amp;DocumentPartId=&amp;Action=Launch), here is my answer to my own question:

The &quot;F&quot; symbol represent an edge-triggering signal
The pulse symbol represents thermal tripping element for overload protection
The &quot;I&gt;&quot; symbol represents electromagnetic tripping element for short-circuit protection
The square represents facility to activate tripping of the two elements above