This telephone circuit was found on a 90's EDN. It keeps a flashing LED to indicate that there was a call in your absence. The components admit equivalents.
circuit is used to increase the sensivity of a relay. A 50 to 100 mA relay can be triggered with...
The configuration shown makes use of a simple source and the gain is given by the relationship between R3...
This blinker consists of a simple multivibrator and instead of the lamp, an LED and a 470 ohms...