This circuit is an improvement over the previous one, using the same capacitor system as a sensor. We also found it in Radio Electronics from the 80s.
This circuit is from a 1980s Motorola documentation. The circuit can be made with modern...
This well-known circuit triggers a relay when light striking the phototransistor is cut off. The...
This circuit generates a pulsed tone whose frequency depends on C2 and whose flashing depends on...