This circuit was found in a 1968 Motorola documentation. The circuit can be implemented with virtually any photo transistor and general-purpose transistor.
In the figure we have the way to configure an OR gate using 3 gates of the 7400. The circuit is...
With this circuit it is possible to implement a wireless ambient sound distribution system using...
This configuration, which can be found in other LM324 manufacturer's manuals, is from the 1982 SGS...