This circuit, suggested by an Electronics World of 1969, keeps a blinking LED for a while when a power outage occurs. Time depends on capacitor C1.
This circuit monitors the humidity of a pot or plant bed, providing indication on two LEDs. The...
This “zero crossing detector” was found in a manual of operational amplifiers from the 1980s....
This narrowband data receiver is from the Philips Databook of 1990. The circuit is powered by 5 V...