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.
This two-tone buzzer can be powered by a solar panel. The circuit is from a 1991 documentation. The...
This blocking oscillator was found in a publication from the 50's. The coils determine the...
The TPA3100D2 integrated circuit from Texas Instruments (www.ti.com) consists of an efficient...