The TAA300 integrated circuit is not common today. In fact, the circuit shown is from a Dutch Philips documentation from 1969. The output is 8 ohm speaker and 9 V power supply.
This basic Schmitt trigger was found in an American publication from 1968. The circuit uses...
This circuit is from an American 1964 documentation. Transistors of the time are used, but modern...
This simple circuit uses small speakers for both listening and speaking (microphone). The feeding is...