Good/Bad Transistor Tester

Good/Bad transistor tester means that this instrument can only determine if the transistor is good or bad, nothing more. Any transistor with gain equal to 30 or more will be considered as good by this tester, and otherwise will be considered as bad. Here is the schematic diagram of the circuit:

To use this instrument, we have to select S2 position according to transistor type (PNP or NPN), then we push the S1 and see if the LED lights. The LED will light if the transistor is good. [Circuit’s schematic diagram source:]