This circuit emits a warning sound when night falls. The circuit is from a Hands On Electronics from the 90s. The Sensor is a common LDR and R6 adjusts the trigger point.
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
This circuit was found in a 1976 NASA manual, making use of components of the time. The transistor...
This circuit is a variation of the common grid dip meter, having been found in a 1975 publication on FETs....