This traditional configuration with the 555 was obtained in an 80s Hands-On Electronics. The relay is of the sensitive type according to the supply voltage.
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...