Transistors are common and when pressing the switch, only one of the LEDs remains lit. What it will be is not possible to predict, which makes the game possible.
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...