This circuit is from a 1969 EEE magazine. The transistors are from that time, but the circuit can be implemented with modern equivalents, such as 2N2646 for Q3.
Found in a 1960 General Electric documentation, this crowbar circuit blows the fuse in case of...
This circuit was originally designed for testing crystals used in color televisions, but it works...
This bridge-biased transistor test circuit measures gain in the range 0 to 300. Circuit is from...