This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
Found in the September 1982 issue of Radio Electronics magazine, this circuit triggers a relay...
The circuit shown has the advantage over the reductions with resistors to have a much higher...
This circuit provides a delay for the activation of an alarm, giving the owner time to leave the...