This unijunction transistor circuit is a frequency divider synchronized to 100 kHz. The circuit was found in a Radio Electronics from July 1968. The adjustment of R4 is important.
This circuit is from a Popular Electronics from the 90s. The integrated circuit admits equivalents...
This very interesting project was obtained in a 1980 publication. It consists of a device that is...
This circuit beeps when the sensor is triggered by the opening of the freezer door or other...