This study explains the breakdown mechanism in different triggered spark gap switches. Two different trigger electrode configurations are tested for the switch predischarge operation in a nitrogen laser circuit. The behavior of the breakdown voltage, when a trigger pulse is applied to the trigger electrode, is investigated, and the results are reported. Based on the experimental measurements new empirical expressions for breakdown voltages are obtained. The self triggered breakdown voltage is also calculated and the differences between the self triggered and external triggered breakdown voltages are reported.