This circuit is from a 90s American documentation. The circuit can use complementary pairs according to the power. The power voltage can be between 5 and 12 V.
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...