This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
This circuit was found in old documentation. PUTs are uncommon components today. The circuit...
This circuit was obtained in a 1991 Electronics Handbook. The publication no longer exists, but...
This crystal oscillator generates a 20 MHz signal. Equivalent transistors such as BF494 and 2N2222...