This circuit uses a 45-0-45 transformer, BD243 transistor, and several other components to control multiple LEDs simultaneously or individually.

The circuit consists of:

45-0-45 transformer (step-up voltage)
BD243 transistor (switching component)
100 ohm resistor (base of transistor)
1N4007 diode (output stage)
160V 100uF capacitor (output stage)
1k ohm resistor (current limiting)
3.7V power supply (positive to transformer, negative to transistor emitter)

The circuit allows for:

Simultaneous lighting of multiple LEDs
Individual lighting of one LED at a time

This versatile circuit is perfect for DIY projects requiring multiple LED control. By adjusting the components and connections, you can customize the circuit to suit your specific needs.