This circuit is from 1999 documentation. However, it can still be easily assembled, as all components used are common. The sensors can have their quantity increased, being connected in parallel.
Frequencies up to just over 100 kHz can be obtained with an oscillator based on one of the four...
This two-transistor circuit is from a Radio Electronics magazine from April 1965. The transistors are...
This traditional monostable configuration is from a Motrorola documentation from the 70s. The...