This simple circuit causes an LED to flash at times whose active cycle is determined by C1 and C2. Transistors can be BC548.
This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's....
This amplifier for audio transmission lines was found in a 1961 American publication. The critical...
Old phones with dials can be used in a simple home intercom system, as this circuit from Popular...