The transistors of this circuit found in a 1965 magazine can be the BC558 and the sensitive 12 V x 50 mA relay. The other components are common.
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...