Single junction transistors, also known as bipolar diodes, have symbols and shapes as shown in the attached drawings.
The method of judging emitter E of single-junction transistor is to place the multimeter in R*100 or R*1K block, the black-meter pen connects the hypothetical emitter, and the red-meter pen connects the other two poles. When there are two low resistances, the black-meter pen connects the emitter of single-junction transistor.
Single junction transistors B1 and B2 are judged by placing the multimeter in R*100 or R*1K block, connecting the emitter with a black-meter pen, and connecting the red-meter pen with the other two poles respectively. In the two measurements, the resistance is high once, and the red-meter pen is connected with the B1 pole.
It should be noted that the above methods for distinguishing B1 and B2 are not necessarily applicable to all single-junction transistors. The forward resistance between E-B1 of individual transistors is small. However, it is not particularly important to accurately determine which pole is B1 and which pole is B2 in practical use. Even if B1 and B2 are reversed, the tube will not be damaged, only the amplitude of the output pulse (single-junction transistors are used as pulse generators). When the output pulse amplitude is found to be small, it is only necessary to adjust the original supposed B1 and B2 pairs.