Bilateral current source 2 (CB20819E)

We found this circuit in an American publication from the 1980s. Equivalent modern operational amplifiers can be used.

Overvoltage protection (CB8360E)
Found in a 1960 General Electric documentation, this crowbar circuit blows the fuse in case of...
Crystal Tester (CB24174E)
This circuit was originally designed for testing crystals used in color televisions, but it works...
Test circuit with bridge (CB22530E)
This bridge-biased transistor test circuit measures gain in the range 0 to 300. Circuit is from...