This automotive grade circuit was found in a 1991 Electronics Hobbyist. The transistors are general purpose types. P1 sets the monitoring voltage.
This circuit can generate 10 MHz signals depending on the crystal and has excellent stability....
This TTL digital circuit from Texas Instruments documentation from the 1970s used the company's SN types...
We found this simple transistor tester in a French publication in 1981. It uses a common analog...