This 80's Hands On Electronics circuit automatically switches from high light to low light when an oncoming car illuminates the sensor. The circuit is powered by the car's own battery.
This is the basic full-scale circuit of an LM3914 for voltage measurement or voltage triggering and...
We found this circuit in the October 1992 Radio Electronics magazine. The frequency is given by C1...
Although most common piezoelectric transducers have a reduction in performance at frequencies...