Now knowing the feet of transistors do not need hard and must use complicated equipment, just with a simple circuit is easily made decisive feet PNP or NPN transistor complete with Base, Collector and Emitter its.
The principle works only utilize reinforcement (high-gain amplifier) that make LED lights up blinking. The trick disconnect one of transistors and then step on the of transistors unknown. If the type NPN (right) corresponding the feet the C-B-E LED will light up.
No need to switch to deactivate the chain of 3Volt DC voltage source, only to pull out one of transistors, the circuit tester is dead. To make the PCB is also fairly easy to quite a line using a cutter knife and then soldering.