The 0 to 50 volt range and 8 ma current maximum range works to protect transistors while experimenting with various transistors. Reducing the 22 K ohm resistor to 10 K ohm will increase maximum current to 15 ma. Observe correct polarity connecting transistor pins to prevent damage.
The 22 K resistor is 2 watt and the 10 K resistor is 3 watt rated. The 50 mfd and 30 mfd capatitors are rated for 150 volts. The diode has about 20 ma range output.
In simulator, switching the base connections of NPN or PNP transistor in curcuit and adjusting the variable 10 k ohm resistor allows you to turn the transistors ON/OFF or control flow through the transistor.
