This circuit was found in a 90s Integrated Circuits Data Book. It interfaces a data line with a CMOS input, being powered by 5V. Can be used as a shield.
This circuit is a from publication 1980, but still can be mounted with BC548 transistors for Q1...
This circuit for testing zener diodes by lifting their curve on an oscilloscope was presented in...
This high quality circuit with complementary symmetry was found in an Electronics World of 1966....