LF sawtooth generator
The most noteworthy element in this circuit is Th1, which is known in data books by no fewer than three different names: thyristor tetrode. programmable uni-junction transistor (PUT) and silicon-controlled switch. In fact, the BRY39 is a fourleyer (p-n-p-n) component. One of the characteristics of this type of component is that the junction of the two outer layers, that is, anode and cathode, begins to conduct when the potential across it exceeds a certain value.