This circuit was obtained in a Hands-On Electronics from the 90's. The circuit turns on one LED at the end of the timer, erasing the other. The timing can be increased by changing C1.
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...