This is a simple high voltage inverter circuit. It is uses NPN transistor type 2N3055. This circuit used to invert low voltage to high voltage. Besides that, this circuit uses flyback transformer that can obtained from B/W or color TV or computer monitor.
R1 (110 Ohm/5W) and R2 (27 Ohm/5W) are used to limit the current so as to reduce load on transistor. In addition, we use L1 to help R1 and R2 reduce the stress on transistor when transistor go into saturation before base drive switces to opposite side. If we use larger flyback or more than 12VDC, we need higher power rating transistors to sustain the operation.