This circuit is from a 1974 publication by Motorola. The unijunction may be 2N2646 and bipolar BC558 and BC548. The pulse duration depends on the capacitor.
The CUT frequency for this filter is determined by the capacitors. The µA4138 is a quad version of...
This circuit was found in the SGS manual of linear integrated circuits of 1982. The circuit...
This circuit turns on your car's backlight when a vehicle coming from behind gets too close to it...