This low frequency divider uses unijunction transistors. The bipolar transistor can be a BC548 and the zener diode Z4XL can be a 12 V zener. The circuit was found in a 1967 publication.
This is another possible version of a negative voltage generator using a 555 integrated circuit. The...
This timer activates a relay after a time interval of up to 15 minutes has elapsed, starting from...
This circuit was used to regulate the speed of small DC motors of cassette recorders. However, if the...