This dual balanced modulator configuration was obtained in a 1980s telecommunications documentation. The circuit makes use of transformers and the diodes are commonly used.
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...