This circuit of a 1969 Electronic Design uses RTL logic. The setting can be adapted to TTL. The frequency is given by the crystal.
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...