This circuit with the PLL4046 was found in the October 1994 Electronics Now magazine. The transistor is low power, and the volume obtained is small.
We found this circuit with transistors in a Philips documentation from 1968. The double transistor...
This circuit, from the ON Semiconductor Thyristor Manual, controls both the speed and direction of...
This circuit was found in a 1978 American publication. It beeps if the car's lights are on and the...