Found ina 1970 American documentation this fast-reading circuit uses a photodiode. Transistors support modern equivalents. The circuit can be used as a shield.
This circuit is designed to activate an automotive alarm after 8 minutes of activation. Of course...
This is one of the channels of an amplifier suggested by Westinghouse in 1970s documentation. The circuit...
This astable multivibrator, well known to all, was found in the Raytheon transistor application manual of...