The voltage boosting in this circuit enable its operation to be powered by 2.5 V rechargeable battery (two cells 1.2V rechargeable batteries),  supplying 400 mA current at 26 V which is needed by the gas arc tube for portable ultraviolet lamp. This inverter circuit has a good efficiency as well, about 80%. Ultraviolet (UV)  light is also known as black light since the light is invisible, but can energize some materials to glow when the materials  is exposed to this black light. Money or other security tag is usually checked used this kind of light. Here is the schematic diagram of the circuit:

BLACK LIGHT INVERTER1 circuit schematic

[Circuit’s schematic diagram source: Motorola Application Notes]