We found this time base of 0.1 to 90 seconds in a circuit manual from the 90s. The single-use transistors used are common and the frequencies given by the adjustment by the potentiometer.
This basic configuration can be found in a lot of articles on this site. In this case, the relay...
This high pass filter was found in the February 1996 Electronics Now magazine. The circuit...
Found in General Electric documentation from 1967, this circuit uses an unusual PUT today. The...