Reference monograph reflecting the almost 60-year period of development and development of one of the oldest negatrons - a single-junction transistor (OPT) and its circuitry analogues. For the first time, along with the description of conventional OPTs (two-base diodes), the latest programmable OPTs, photo-OPT optons integrated with the OPT thyristor, integrated OPT functional circuits, OPT transistor analogues and numerous applications of devices of this class are described in detail. Along with the advantages of the devices, their disadvantages and limitations are objectively described.