Final answer:
The R on T phenomenon occurs when pacemaker depolarization is initiated during the relative refractory period [T wave].
Step-by-step explanation:
The R on T phenomenon, also known as pacemaker depolarization initiated during the relative refractory period [T wave], can be caused by certain settings. However, the question does not provide options for the possible settings. To better answer your question, please provide the possible settings you are referring to, and I will be happy to assist you further.